WO2008053479A1 - Self-immolative polymers - Google Patents

Abstract

Self-immolative polymers, designed to release a chemical moiety, or a plurality of chemical moieties, upon a pre-determined cleavage event, or sequences of events, are disclosed. The polymers can be simple polymers, comb polymers or branched polymers. Further disclosed are methods of usage, compositions and articles-of-manufactures containing the self-immolative polymers, and processes for preparing the same.

Description

SELF-IMMOLATIVE POLYMERS

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to novel self-immolative systems and, more particularly, to self-immolative polymers and comb-polymers which are designed to release a chemical moiety, or a plurality of chemical moieties, upon a pre-determined cleavage event, or a sequence of events, and can therefore be used beneficially in, for example, a variety of therapeutic, diagnostic and other industrial applications.

The increasing interest in diagnostics, imaging and drug delivery systems generates a continuous need for the development of new platforms for the amplification of molecular signals. A novel concept describing the design and synthesis of dendritic structures with a trigger that initiates the fragmentation of the dendrimer molecule into its building blocks in a self-immolative manner with the consequent release of the tail-group units, has been recently disclosed. This concept exploits the fact that the dendrimer skeleton can be constructed in such a way that it can be made to disintegrate into known molecular fragments once the disintegration process has been initiated.

Macromolecules that are designed so as to self-immolate upon a pre-determined cleavage event are highly advantageous, in addition to their use in therapeutic and diagnostic application, in various industrial applications. These include, for example, medical devices, as well as disposable plastic and sanitary products, and the like.

Based on this concept, self-immolative dendritic prodrug systems have been developed as presented, for example, in WO 2004/019993. These systems are based on the incorporation of drug molecules as end or tail units and the use of an enzyme substrate as another end unit which serves as the trigger that generates a multiple-prodrug unit release process that is activated by this single enzymatic cleavage and propagates spontaneously. Following the same paradigm, fully biodegradable dendrimers that are disassembled through multi-enzymatic triggering followed by self-immolative chain fragmentation were also designed and practiced.

The concept of multi-triggered, self-immolative dendron was recently applied to synthesis of a prodrug activated through a molecular "OR" logic trigger (a dual-trigger activated by either one of two different enzymes).

Such self-immolative dendritic prodrug systems were shown to have a significant advantage in tumor cell-growth inhibition compared with classical monomeric prodrugs.

Furthermore, a single-triggered hetero-dimeric prodrug with the anticancer agents doxorubicin and camptothecin has been designed and practiced, enabling, for the first time, the simultaneous release of two different chemotherapeutic drugs at the same location.

Various aspects and embodiments of self-immolative dendrimers are described, for example, in WO 2004/019993, U.S. Patent Application No. 2005/0271615 and U.S. Patent Application No. 2006/0269480. The teachings of these patent applications are incorporated herein by reference as if fully set forth herein. SUMMARY OF THE INVENTION

Self-immolative polymeric molecules, which are useful, for example, as molecular delivery vehicles or in disposable articles of manufacturing, are presented herein. The self- immolative polymers presented herein are designed to disassemble into molecular fragments once the disassembly process has been initiated by a triggering event, and thereby release at least one, and preferably a plurality, of releasable units. The triggering event which starts the break-down (disintegration) process of the self-immolative polymer can occur as a result of cleavage of one or more cleavable triggering units, which can be similar or different. Selective cleavage of the cleavable triggering unit(s) initiates the polymer fragmentation into its building blocks and the release of the releasable units. The self-immolative polymers presented herein can be designed to possess a simple linear polymer having at least one releasable unit attached to one end thereof (see, Figure 1), a branched polymer having more than one releasable units attached at the ends of each of the branches, or a comb-polymer having periodic branching units, each having at least one releasable unit attached to its end (see, Figures 2 and 3, respectively).

The polymers can thus be used, for example, in methods of treating various medical conditions, in diagnostic methods, and in methods for detecting various substances.

The polymers can be further used in the manufacture of various products, such as diapers, plastics and medical devices. According to an aspect of some embodiments of the present invention there is provided a polymer which includes one or more cleavable triggering unit, one or more releasable unit and a plurality of building units, the plurality of building units being linked to one another so as to form a self-immolative polymeric backbone, the polymeric backbone carries the cleavable triggering unit and the releasable unit, the cleavable triggering unit and the self-immolative polymeric backbone being such that upon cleavage of the cleavable triggering unit, the self-immolative polymeric backbone self-immolates, thereby releasing the one or more releasable unit.

According to some embodiments of the invention, each of the building units in the self-immolative polymeric backbone independently has a general formula selected from the group consisting of Formula Ia and Formula Ib, as presented herein.

Hence, according to an aspect of some embodiments of the present invention there is provided a polymer which includes one or more cleavable triggering unit, one or more releasable unit and a plurality of building units, the plurality of building units being linked to one another so as to form a self-immolative polymeric backbone which carries the cleavable triggering unit and the releasable unit, each of the building units in the self-immolative polymeric backbone independently has a general formula selected from the group consisting of Formula Ia and Formula Ib:

Formula Ia Formula Ib

wherein:

V is O, S₁ PR⁶ or NR⁷; U is O, S or NR⁸;

A, B, D and E are each independently a carbon atom or a nitrogen atom; R¹, R², R³, R⁴ and R⁵ are each independently

_ hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, or alternatively, two or more of R¹, R², R³, R⁴ and R⁵ being connected to one another to form an aromatic or aliphatic cyclic structure; whereas: a, b and c are each independently as integer of 0 to 5;

K is O. S, PR⁶ Or NR⁷; and

I, F and G are each independently -R¹¹C=CR¹²- or -C≡C-, where each of R¹¹ and R¹² is independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, or, alternatively, R¹¹ and R¹² being connected to one another to form an aromatic or aliphatic cyclic structure; and

R⁶, R⁷ and R⁸ are each independently hydrogen, alkyl, aryl, cycloalkyi, heterocycloalkyl, heteroaryl, aikoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, provided that one or more of R^R³ in Formula Ia and of R¹-R^ε in Formula Ib is

the cleavable triggering unit and the self-immolative polymeric backbone being such that upon cleavage of the cleavable triggering unit, the self-immolative polymeric backbone self-immolates, thereby releasing the one or more releasable unit.

According to some embodiments of the invention, the polymer includes a plurality of releasable units which are all the same or different.

According to some embodiments of the invention, the polymer includes a plurality of cleavable triggering units, the cleavable triggering units which are all the same or different. According to some embodiments of the invention, the cleavable triggering units are different, and two or more of the cleavable triggering units are cleavable upon a different event.

According to some embodiments of the invention, the polymer includes one or more self-immolative spacer. According to some embodiments of the invention, the spacer links one or more of the cleavable triggering unit(s) and one or more of the building units in the self-immolative polymeric backbone.

According to some embodiments of the invention, one or more of the spacer(s) links one or more of the releasable units and one or more of the building units in the self- immolative polymeric backbone.

According to some embodiments of the invention, the spacer links two or more of the building units.

According to some embodiments of the invention, one or more of the cleavabie triggering units, one or more of the spacers and the building units are such that upon cleavage of the cleavable triggering unit, the self-immolative polymeric backbone and the spacer(s) self-immolate to thereby release the all the releasable units.

According to some embodiments of the invention, one or more of the building units in the self-immolative polymeric backbone has two or more releasable units linked thereto.

According to some embodiments of the invention, each of the building units in the self-immolative polymeric backbone has two or more releasable units attached thereto.

According to some embodiments of the invention, one or more of the cleavable triggering unit is selected from the group consisting of a photo-labile triggering unit, a chemically removable triggering unit, a hydrolizable triggering unit and a biocleavable triggering unit. According to some embodiments of the invention, one or more of the releasable unit is selected from the group consisting of a detectable agent, a therapeutically active agent, a second self-immolative compound, a chemosensitizing agent, a targeting moiety, an agrochemical, a chemical moiety and a chemical reagent.

According to some embodiments of the invention, one or more of the cleavable triggering units is a biocleavable triggering unit and one or more of the releasable units is an agent selected from the group consisting of a therapeutically active agent, a chemosensitizing agent, a targeting moiety and a detectable agent.

According to some embodiments of the invention, the biocleavable triggering unit is an enzymatically cleavable triggering unit.

According to some embodiments of the invention, the therapeutically active agent is a chemotherapeutic agent.

According to some embodiments of the invention, one or more of the cleavable triggering units is a photo-labile triggering unit and at least one of the releasable units is a detectable agent.

According to some embodiments of the invention, one of the cleavable triggering units is a hydrolyzable triggering unit and the releasable unit is an agrochemical.

According to some embodiments of the invention, one of the cleavable triggering units is a chemically removable triggering unit and the releasable unit is a detectable agent.

According to some embodiments of the invention, the detectable agent is selected from the group consisting of fluorescent agent, a radioactive agent, a magnetic agent, a chromophore, a phosphorescent agent, a contrast agent and a heavy metal cluster.

According to some embodiments of the invention, the self-immolative polymeric backbone is selected from the group consisting of a polycarbamate, a polycarbonate, a polyether and a polyurethane.

According to some embodiments of the invention, one or more of the building units has the general Formula Ib.

According to some embodiments of the invention, V is O or S; each of B and D is a carbon atom; each of R¹, R² R⁴ and R⁵ is independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, or alternatively, two or more of R², R³ and R⁴ being connected to one another to form an aromatic or aliphatic cyclic structure; and R³ is

According to some embodiments of the invention, each of R¹, R² R⁴ and R⁵ is independently hydrogen or alkyl; each of a, b and c equal 0; and each of R⁹ and R¹⁰ is independently hydrogen or alkyl.

According to some embodiments of the invention, the self-immolative spacer has a general formula selected from the group consisting of Formula Ha, Formula lib, Formula Hc, Formula Hd:

Formula Ha Formula lib

Formula He Formula Hd

and a combination thereof, wherein: d, e, f, g and h are each independently an integer from 0 to 3, provided that d + e + f

≥ 2;

R¹² and R¹³ are each independently hydrogen, alkyl or cycloalkyl; and R¹⁴, R¹⁵, R¹⁶, R¹⁷, R¹⁸ and R¹⁹ are each independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate.

According to some embodiments of the invention, the polymer is having a general formula selected from the group consisting of:

Q - A₁ - [X-YJn -A₂ - W Q - A₁ - [X(W)m-Y]n-1 - Xn

Formula Ilia Formula IHb

wherein: n is an integer from 2 to 10⁵; m is an integer from 1 to 4;

Q is the cleavable triggering unit; A₁ and A₂ are each independently the self-immolative spacer or absent;

X is the building unit;

Y is the self-immolative spacer or absent; and

W is the releasable unit. According to an aspect of some embodiments of the present invention there is provided a polymer which includes a plurality of building units linked to one another, each of the building units independently having a general formula selected from the group consisting of Formula Ia and Formula Ib, as described herein.

According to some embodiments of the invention, each of the building units has the general Formula Ib.

According to some embodiments of the invention, V is O or S; each of B and D is a carbon atom; each of R¹, R², R⁴ and R^s is independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, or alternatively, two or more of R², R³ and R⁴ being connected to one another to form an aromatic or aliphatic cyclic structure; and

R³ is

According to some embodiments of the invention, each of R¹, R², R⁴ and R⁵ is independently hydrogen or alkyl; each of a, b and c equal 0; and each of R⁹ and R¹⁰ is independently hydrogen or alkyl.

According to an aspect of some embodiments of the present invention there is provided a composition which includes any of the polymers described herein. According to some embodiments of the invention, the releasable unit includes a therapeutically active agent and the cleavable triggering unit is a biocleavable triggering unit, the composition being a pharmaceutical composition which further includes a pharmaceutically acceptable carrier.

According to some embodiments of the invention, one of the therapeutically active agent is selected from the group consisting of an anti-proliferative agent, an anti-inflammatory agent, an antibiotic, an anti-viral agent, an anti-hypertensive agent, a chemosensitizing agent and a combination thereof.

According to some embodiments of the invention, the composition is packaged in a packaging materia! and identified in print, in or on the packaging material, for use in the treatment of a disease or disorder treatable by the therapeutically active agent. According to some embodiments of the invention, the releasable unit is a detectable agent, the composition is useful in a diagnostic and/or analytical application.

According to some embodiments of the invention, the releasable unit is an agricultural agent and the cleavable triggering unit is a hydrolyzable triggering unit, the composition is useful as an agricultural composition which further includes an agriculturally acceptable carrier.

According to an aspect of some embodiments of the present invention there is provided an article-of-manufacture which includes any one or a combination of the polymers as presented herein. According to some embodiments of the invention, the article-of-manufacture is selected from the group consisting of a medical device, a disposable plastic product, a disposable women's sanitary item, a diaper, a disposable medical supply, a disposable food container or dish, a disposable item of clothing and a disposable cutlery item.

According to an aspect of some embodiments of the present invention there is provided a use of the composition of claim 34 as a medicament for treating a condition that is treatable by the therapeutically active agent.

According, to an aspect of some embodiments of the present invention there is provided a process of preparing the self-immolative polymer as presented herein, the process is effected by: polymerizing the plurality of building units; attaching the one or more releasable unit to one or more of the plurality of building units; and attaching the one or more cleavable triggering unit to the polymeric backbone.

According to some embodiments of the invention, attaching the releasable unit to one or more of the plurality of building units is performed prior to the polymerizing.

According to some embodiments of the invention, one or more of the plurality of building units has one or more building unit attached thereto prior to the polymerizing.

According to some embodiments of the invention, attaching the one or more releasable unit to one or more of the plurality of building units is performed prior to the polymerizing.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting. BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

In the drawings:

FIG. 1 presents a schematic illustration of the construction of a self-immolative linear polymer having a cleavable triggering unit and a releasable unit (denoted "reporter") according to embodiments of the present invention; FIG. 2 presents a schematic illustration of the construction of a self-immolative comb polymer having a cleavable triggering unit and a plurality of releasable units (marked by an R in a red circle) according to embodiments of the present invention;

FIG. 3 presents a schematic illustration of an exemplary self-immolative branched polymer according to embodiments of the present invention, having a cleavable triggering unit and a backbone of repeating branching units, each carrying at least two reporter groups;

FIGs. 4a-b present schematic illustrations of the design and disassembly mechanism of two exemplary self-immolative polymers according to embodiments of the present invention: a polycarbamate self-immolative polymer (Figure 4a) and a polycarbonate self- immolative polymer (Figure 4b); FIGs. 5a-b present schematic illustrations of the synthesis of an exemplary self- immolative polymer having a cleavable triggering unit, Compound 1 (Figure 5a), and the chemical scheme of the synthesis of the corresponding monomer precursor, Compound 5 (Figure 5b);

FIGs. 6a-b present the mass spectrum analysis of an exemplary self-immolative polymer (Figure 6a) and the chemical structures of the oligomers detected in the MS spectrum;

FIG. 7 presents a schematic illustration of the synthesis of an exemplary self- immolative comb polymer having a cleavable triggering unit, according to embodiments of the present invention; FIG. 8 presents a schematic illustration of the disassembly mechanism of an exemplary self-immolative comb polymer according to embodiments of the present invention, constructed from repeating branching units, each having one "head" and three "tails", also referred to herein as an AB₃ unit or monomer; FIG. 9 presents a schematic illustration of the synthesis of another exemplary self- immolative comb polymer having a cleavable triggering unit according to embodiments of the present invention;

FIG. 10 presents a schematic illustration of the polymerization process in the preparation of an exemplary self-immolative branched polymer having a cleavable triggering unit according to embodiments of the present invention;

FIG. 11 presents a schematic illustration of the activation and subsequent cascade break-down of an exemplary self-immolative branched polymer according to embodiments of the present invention (Compound 18), which releases a plurality of 5-amino-2-nitro-benzoic acid reporter groups (Compound 19), after a triggering event effected by penicillin-G-amidase

(PGA) which cleaves off the cleavable triggering unit phenylacetamide (marked in red);

FlG. 12 presents a schematic illustration of the activation and subsequent cascade break-down of an exemplary self-immolative comb polymer according to embodiments of the present invention (Compound 20), which releases a plurality of molecules of the anticancer drug doxorubicin (DOX) after a single triggering event effected by peniciliin-G-amidase (PGA) which cleaves off the cleavable triggering unit phenylacetamide (marked in red);

FIG. 13 presents a schematic illustration of the conversion of camptothecin (Compound 21) into a suitable reporter group according to the present embodiments, by using N,N-dimethylethylene-diamine as a self-immolative spacer, linking between a hydroxy group inherent to the drug molecule, and the polymeric backbone;

FIG. 14 presents a schematic illustration of a water-soluble self-immolative comb polymer wherein hydrophilic moieties (marked in green) are attached thereto in a similar manner to the attachment of the reporter groups (marked in blue);

FIG. 15 presents a schematic illustration of a PGA-triggered release of tryptophan through an exemplary self-immolative trimer according to the present embodiments;

FIG. 16 presents a plot of the fluorescence intensity change at λem of 500 nm monitored during the disintegration process of the exemplary water-soluble self-immolative polymer (concentration 500 μM), releasing (4-amino-3-((E)-3-(carboxylic acid)prop-1- enyl)phenyl)methanol upon disintegration (λex = 270 nm, marked in circles), triggered by the enzymatic cleavage of the end carbamate conducted in borax buffer solution pH 8.5 containing BSA (10 mg/ml, the blank solution for calibration marked in squares); and

FIGs. 17a-b present comparative plots following the release of p-nitroaniϋne and tryptophan effected by the enzymatically catalyzed disintegration of Compound 23, an exemplary self-immolative polymer according to embodiments of the present invention, following the increase in the absorbance intensity (

representing the release of p- nitroaniline by the catalytic triggering event effected by BSA (blue line in Figure 17A), as compared to the absorbance intensity change in the control solution that contains no protein (red line in Figure 17A), and by following the conversion of Compound 23 (red line in Figure 17B) to tryptophan (blue line in Figure 17B) as monitored by HPLC. DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is of self-immolative polymers which can be used as molecular delivery vehicles in various therapeutic (e.g., prodrugs), diagnostic (e.g., molecular reporting signal amplifier), agricultural (e.g., delivery of agrochemicals) and other industrial applications. The self-immolative polymers are designed to disassemble into small fragments and thereby release one or more releasable units. The disassembly process is triggered by a trigerring (e.g., chemical) event which cleaves off one or more cleavable triggering unit from the polymer to thereby commence its simultaneous disassembly. The triggering event can be, for example, a photochemical event, a metabolic process catalyzed by one or more enzymes (a multi-enzymatic triggering mechanism), a single chemical event or a sequence of chemical events. The present invention is further of processes of preparing these self-immolative polymers, of articles-of-manufacturing containing same and of uses thereof. The present invention is further of polymers made from the newly designed building units described herein. The principles and operation of embodiments of the present invention may be better understood with reference to the drawings and accompanying descriptions.

Before explaining at least one embodiment of the invention_^ in detail, it is to be understood that the invention is not limited in its application to the details set forth in the following description or exemplified by the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

As described hereinabove, most of the presently known amplified molecular delivery and signaling systems utilize compounds that possess a plurality of functionalities to which a plurality of releasable tail groups are attached. Releasing the releasable tail groups involves a cleavage event for each and every releasable tail group. It is clear that these systems suffer from great inefficiency in the release process.

The present inventors have now designed and practiced novel self-immolative compounds that are capable of releasing a plurality of functional moieties simultaneously, and which have a compact molecular cross-section. More specifically, the present inventors have designed, prepared and practiced polymers that include a self-immoiative polymeric backbone provided with at least one cleavable triggering unit, and which carry at least one and preferably a plurality of releasable units as the tail units. These polymers afford a molecular delivery vehicle which releases its cargo simultaneously upon a single, pre- determined triggering event.

While reducing the present invention to practice, the present inventors have prepared a series of self-immolative polymers, designed as described herein, which are capable of releasing a plurality of functional tail groups, or releasable units upon a single cleavage event.

Hence, according to an aspect of the present invention, there is provided a polymer which includes at least one cleavable triggering unit, at least one releasable unit and a plurality of building units. The building units of the polymer presented herein are linked to one another so as to form a self-immolative polymeric backbone, which carries the cleavable triggering unit(s) and the releasable unit(s). According to the present embodiments, the cleavable triggering unit and the self-immolative polymeric backbone are designed such that upon cleavage of the cieavable triggering unit, the self-immolative polymeric backbone self- immolates in a cascade-like disassembly process, thereby releasing all the releasable unit(s) simultaneously.

The term "plurality", as used herein, means at least two.

The term "polymer" as used herein, refers to a compound composed of repeating chemical building units that are connected to one another by covalent bonds to thereby form a polymeric backbone. A linear polymer is the simplest form of a polymeric molecule and the linear trait relates to its backbone which is a single main chain. According to the present embodiments, a polymer can be substantially unbranched chain polymer which is characterized by its persistence length, or a branched polymer molecule which is composed of a main chain with one or more substituent side chains or branches, as well as cross-linked polymers. A particular example of a branched polymer is a comb polymer, having a repeating periodical branching moiety along the main chain or backbone. The term "polymer", as used herein, refers to a compound that comprises at least two building units that form a polymeric backbone. The phrase "building unit", also referred to herein as "monomer" or "monomeric unit", as used herein, describes a unit that, when linked to other same or different units, forms a polymeric backbone.

The term "polymer", as used herein, does not encompass and specifically excludes some particular types of non-linear compounds, which can be considered as private cases of branched polymers, such as dendrimers, star polymers, dendronized polymers, hyper- branched polymers and brush-polymers (also called bottle-brushes).

In contrast to polymers, dendrimers, dendronized polymers, hyper-branched polymers and brush-polymers are repeatedly cascade-branched molecular species which, in some cases, also possess internal structural perfection. Dendrimers and dendrons are monodisperse, and usually highly symmetric compounds which contain a single chemically addressable group that is called the focal point. In general, dendritic compounds comprise a core and/or a focal point and a number of generations of ramifications (also known and referred to as "branches" or "branching units") and an external surface. The generations of ramifications are composed of repeating structural units, which extend outwards radially from the core or the focal point. Dendrimers are also referred to in the art as molecules that form a tree-like structure and are built from several dendron units that are all connected to a core unit via their focal point. Dendritic macromolecules typically possess a perfectly cascade- branched, highly defined, synthetic structure, characterized by a combination of high-group functionalities and a compact molecular structure. Because of the lack of the molar mass distribution high molecular weight dendrimers and dendrons are macromolecules but are not considered polymers by persons skilled in the art.

As used herein, the phrase "polymeric backbone" describes the polymeric chain formed from all of the monomeric units (building units) composing the polymer, including the terminal building units and, the intermediary building units and the building units of any branch of the polymer.

As defined herein, the polymer described herein is constructed from two or more building units which form the polymeric backbone, one or more triggering unit(s) and one or more releasable unit(s). The polymeric backbone carries the trigerring units(s) and the releasable unit(s). The term "carries" and its grammatical diversions, as used herein, means that the triggering unit(s) and the releasable unit(s) are attached, via a chemical bond (e.g., covalent bond), to the polymeric backbone, i.e., to the building units which compose the polymer.

Hence, the polymeric backbone of the polymer is an allegoric term which refers to the trace of the polymer which follows the series of covalently bonded atoms that together create the continuous chain of the molecule together with any possible branches it may have. Therefore, according to embodiments of the present invention, the. triggering unit(s) and the releasable unit(s) can be attached, directly or indirectly, to any building unit that forms a part of the polymeric backbone. According to some embodiments, at least one of the triggering units is attached to a terminal building unit in such a position which enables the disassembly process to start at that terminus and progress along the entire polymeric backbone.

According to some embodiments, the releasable units can be attached to any of the building units, including the terminal building units and the intermediary building units. For example, the polymer may be a dimer (2 building units long), having at least one triggering unit which is attached to one building unit, and at least one releasable unit which is attached to the other building unit (a simple linear polymer).

In another example, the polymer is a trimer, having at least one triggering unit which is attached to one of the terminal building units, and at least one releasable unit which is attached to each of the building units, including both terminal building units (a comb polymer). The phrase "cleavable triggering unit", also referred to herein as "triggering unit", describes a moiety of a compound that can be cleaved off the self-immolative polymer as a result of an interaction with or exposure to a corresponding trigger or a triggering event, and thereby initiates the self-immolation process. Therefore, the term "trigger" as used herein refers to an entity or an event (a triggering event) that effects the cleavage of the cleavable triggering unit described above from the polymer to which it is attached.

The cleavable triggering unit according to the present embodiments can be, for example, a photo-labile triggering unit that is cleaved upon its exposure to a trigger in the form of light or otherwise electromagnetic radiation; a chemically removable triggering unit that is cleaved upon a trigger in the form a chemical reaction, such as a hydrolysable triggering unit that is cleaved upon reacting with a water molecule. Alternatively or in addition, the cleavable triggering unit according to the present embodiments can be a biocleavable moiety that is cleaved upon a biological reaction with the appropriate trigger in the form of a biological catalyst.

Preferred biological catalysts according to the present embodiments are enzymes, whereas the cleavable triggering units are the corresponding enzymatic substrates. Alternatively, biocleavable triggering units can be acid-labile triggering units, that can be removed in the presence of an acidic environment, e,g., in the gastrointestinal tract. In preferred embodiments the polymer contains a biocleavable triggering unit, such that the cleavable triggering unit is a substrate of a naturally occurring enzyme. The cleavage of a biocleavable triggering unit (the triggering event) is therefore an enzymatic reaction, which can take place at a specific bodily site(s) where a particular enzyme (or enzymes) is expressed or over-expressed. Therefore the triggering event can be selected such that it will occur at a pre-selected type of tissue or type of cells, thereby bestowing a targeting quality to the self-immolative polymer. This site-specific seif-immolative polymer can be made even more specific when using a polymer which contains a sequence of two or more biocleavable (enzyme substrate) triggering units. In such cases two or more corresponding enzymes will initiate the disintegration cascade only when the polymer is subjected to a triggering event effected by all these enzymes in a sequence of triggering events (corresponding to the sequence of chain of the biocleavable triggering units on the polymer).

Non-limiting examples of photo-labile triggering units, which are cleaved upon exposure to light or any other energy source, include peroxides (having an -O-O- bond), ketones (undergoing cleavage via Norish type reactions), and 2-nitrobenzyl alcohol and derivatives thereof (commonly used in organic syntheses as photo-iabile groups).

Non-limiting examples of chemically removable triggering units, which are cleaved upon a chemical reaction, include esters, thioesters, amides, thioamides, and the like.

Non-limiting examples of cleavable triggering units which are enzymatic substrates include any particular or generic form of a short peptide, which will be cleaved off by a corresponding or generic protease-type enzyme that can catalyze proteolysis, namely the hydrolysis of the peptide bond that links one of the amino acids of the peptide to the polymer. Using a peptide as a triggering unit bestows specificity to the polymer in terms of the conditions which are required for its self-immolation process, namely the occurrence of a contact between the polymer and a specific enzyme or a group of enzymes. Similarly, other specific non-peptide enzyme substrates can be used such as, for a non-limiting example, the cleavable triggering unit phenylacetamide which is cleavable by the enzyme penicillin-G- amidase (PGA), as demonstrated and exemplified in the Examples section that follows below.

These and other preferred features of the triggering units and their corresponding triggers as described herein are also taught, for example, in WO 2004/019993, U.S. Patent Application No. 2005/0271615 and U.S. Patent Application No. 2006/0269480. As presented hereinabove, the self-immolative polymers of the present invention are highly advantageous as being capable of releasing a plurality of releasable units both efficiently and simultaneously.

As used herein the term "simultaneously" is used to indicate a multi-cascade response to a single trigger event.

As used herein, the phrase "single trigger event" is used to describe an event which initiates the multi-cascade response. The phrase "single trigger event" encompasses events which include a series of events which lead to the initiation of the multi-cascade response. For example, the multi-cascade response is the disassembly of the entire self-immolative polymer, which is initiated by the cleavage of a cleavable triggering unit that is afforded by cleavage of another cleavable triggering unit attached to the former unit. In this example, the single trigger event includes two cleavage processes which together lead to a cascade disassembly response.

According to embodiments of the present invention, at least two triggering units of the plurality of triggering units are each cleavable upon a different triggering event. The presence of two or more such cleavable triggering units enables to polymers that release one or more chemical moieties upon a combination of cleavage events that lead to cleavage of two or more of the cleavable triggering units (a molecular AND logic gate), as is detailed hereinabove. In cases where the self-immolative polymer is required to be highly specific and targeted with respect to a particular environment, such as in the case where the polymer serves as a tissue- or cell-targeted drug delivery prodrug, the self-immolative polymer presented herein can be designed so as to have more than one and optionally different cleavable triggering units which enable to activate the release mechanism only in the presence of a specific combination of triggers, each effects a different cleavage process.

This particular configuration referred to as an AND-gated process is afforded when more than one type of cleavable triggering units are linked to one another in a chain having a predetermined sequence. The triggering event is then required to be composed of several sub-triggering events wherein the cleavage of one of the cleavable triggering units must occur before the other cleavable triggering unit is cleaved, and only the cleavage of all cleavable triggering units can initiate the disintegration cascade.

When the cleavable triggering units are such that require an enzymatic cleavage event (biocleavable triggering units), and each requires contacting a different enzyme, only the presence of all enzymes in the path of the polymer will initiate the cascade once the last sub-triggering event has occurred. This configuration can be regarded as a biologic molecular AND logic gate, which enhances the specificity of the release mechanism, rendering these self-immolative polymers as highly suitable for a variety of pharmaceutical, analytical, diagnostic and biological applications. Thus, according to embodiments of the present invention, the self-immolative polymers presented herein are having more than one cleavable triggering unit, and each of the cleavable triggering units can be different

The phrase "releasable unit" is also referred to herein as "releasable chemical moiety", "reporter group", "tail unit" and "head group". This phrase is used to describe a moiety of a chemical compound, which, once being attached to the polymers described herein, can be released upon a sequence of events (e.g., trigger-induced cleavage and subsequent self-immolation of the entire polymer) initiated by the triggering event, to generate (release) the chemical compound. Preferred features of the releasable chemical moieties and functional groups described herein are also taught, for example, in WO 2004/019993, U.S. Patent Application No. 2005/0271615 and U.S. Patent Application No. 2006/0269480.

As is known in the art, self-immolative systems and processes typically involve electronic cascade self-elimination and therefore self-immolative systems and processes typically include electronic cascade units which self-eliminate through, for example, linear or cyclic 1,4-elimination, 1 ,6-elimination, etc. Such electronic cascade units are described in the art (see, for example, WO 02/083180 and U.S. Patent Application 2005/0271615).

Hence, in the context of the present invention, the phrase "building unit" refers to a monomeric unit which is used to form a self-immolative polymer that can undergo a self- immolative cascade disassembly, or self-immolate.

The building unit presented herein may have two or more extension positions from which the main chain can be elongated, branched or attached to a cleavable triggering unit, a releasable unit or a self-immolative spacer, as described hereinbelow. In one embodiment, the building unit exhibits four such extension positions which can be allocated to link another building unit, a cleavable triggering unit, a releasable unit and/or a self-immolative spacer. This unit is also referred to herein as an AB₃ unit, having one "head" and three "tails".

According to embodiments of the present invention, each of the building units in the self-immolative polymeric backbone presented herein independently has a general formula which is selected from the group consisting of Formula Ia and Formula Ib:

Formula Ia Formula Ib wherein:

V is O, S, PR⁶ or NR⁷; U is O, S or NR⁸;

A, B, D and E are each independently a carbon atom or a nitrogen atom; R¹, R², R³, R⁴ and R⁵ are each independently

_ hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic aikylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfinate, sulfinyl, phosphonooxy or phosphate, or alternatively, at least two of R¹, R², R³, R⁴ and R⁵ being connected to one another to form an aromatic or aliphatic cyclic structure; whereas: a, b and c are each independently as integer of 0 to 5; K is O, S, PR⁶ or NR⁷; and

I, F and G are each independently -R¹¹C=CR¹²- or -C≡C-, where each of R¹¹ and R¹² is independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic aikylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfinate, sulfinyl, phosphonooxy or phosphate, or, alternatively, R¹¹ and R¹² being connected to one another to form an aromatic or aliphatic cyclic structure; and R⁶, R⁷, R⁸, R⁹ and R¹⁰ are each independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic aikylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfinate, sulfinyl, phosphonooxy or phosphate, provided that at least one of R¹-R³ in Formula Ia and of R¹-R⁵ in Formula Ib is said

In some embodiments, the V represents a group that links the building unit to either another building unit, to a releasable unit, or to a self-immolative spacer. As is described hereinabove, V can be an etheric group (-O-), a thioetheric group (-S-), a substituted or non- substituted amino group (-NR⁶-) or a substituted or non-substituted phosphinic group (-PR⁷-). In some embodiments, the building units is linked to either the cleavable triggering unit(s), the releasable unit(s), or the self-immolative spacer(s) via one or more

groups, wherein K is O or NH. The -(l)a-(F)b-(G)c- unit, if present, is a linear electronically-conjugated unit that is conjugated to the aromatic system of the building unit and thereby directly participates in the self-immolative reactions cascade, whereas the carboxy unit -0-(C=O)- enables the release of either the cleavable triggering unit(s), the releasable unit(s), or the self-immolative spacer(s) which are attached thereto, via a decarboxylation process. The presence of one or more such

groups (with K being O or NH) as substituents of the aromatic system enables the occurrence of more than one self-immolative reactions sequence at a time. The aromatic system, while being capable of undergoing various rearrangements, further enables such occurrence. However, as such rearrangements are more facilitated in a six-membered aromatic ring, the building unit preferably has the general Formula Ib.

Hence, preferably at least two of the rings substituents R¹, R², R³, R⁴ and R⁵ in

Formula Ib are

, wherein K is O or NH, and more preferably K is NH.

Further preferably, at least two of R², R³ and R⁴ are

, wherein K is O or NH, and more preferably K is NH.

Other ring substituents, as well as the other substituents in Formulas Ia and Ib, namely R¹ and R⁵-R¹², can be hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxylate, sulfate, sulfonyl, sulfinyl, phosphonate or phosphate, as these terms are defined herein.

Alternatively, at least two adjacent substituents of R¹, R², R³, R⁴ and R⁵ can be connected to one another, so as to form an aromatic or aliphatic cyclic structure. Thus, for example, the self-immolative spacer comprises an aromatic system that include two or more fused rings (e.g., naphthalene or anthracene), or an aromatic ring that is fused to one or more alicyclic rings.

According one embodiment, the building unit has the general Formula Ib, wherein V is O or S, each of B and D is a carbon atom, each of R¹ and R⁵ is hydrogen or alkyl, a, b and c are all 0 and R⁹ and R¹⁰ are hydrogen or alkyl.

In another embodiment, the building unit has the general Formula Ib, wherein V is O, B and D are each carbon atoms, R¹, R², R⁴, R⁵, R⁹ and R¹⁰ are each hydrogen and R³ is

whereas a, b and c are each 0. Such a building unit, upon self-immolation, generates CO₂ and (4-aminophenyl)methanol (see, Compound 4 in Figure 4a).

In yet another embodiment, the building unit has the general Formula Ib, wherein V is O, B and D are each carbon atoms, R¹, R², R⁴, R⁵, R⁹ and R¹⁰ are each hydrogen and R³ is

whereas a, b and c are each O. Such a building unit, upon self-immolation, generates CO₂ and 4-(hydroxymethyl)phenol (see, Compound 3b in Figure 4b).

As presented hereinabove, the various units in the self-immolative polymer presented herein may be linked by a self-immolative spacer.

As is well known in the art, the term "spacer" describes non-functional moiety, which is incorporated in a compound in order to facilitate its function and/or synthesis. The self-immolative spacer according to the present embodiments may link between any two of the various units of the polymer as presented herein, such as, for example, between two of the building units in the self-immolative polymeric backbone; link one or more of the cleavable triggering units to one or more of the building units in the self-immolative polymeric backbone; and/or link one or more of the releasable units to one or more of the building units in the self-immolative polymeric backbone. Similarly the self-immolative spacer can link between two cleavable triggering units and/or between two releasable units.

Incorporation of a self-immolative spacer between the building unit(s) and one or more of the cleavable triggering units provides for and determines the distance therebetween.

Such a distance is oftentimes required to facilitate the cleavage of the cleavable triggering unit by rendering the cleavable triggering unit unhindered and non-rigid and thus exposed and susceptible to interact with the other factors which affect its cleavage. For example, a spacer will extrude-out a substrate-type cleavable triggering unit, rendering it more susceptible to an enzymatically catalyzed cleavage reaction. Incorporation of a self-immolative spacer between the releasable unit(s) or the cleavable triggering unit(s) and the building units can be performed so as to facilitate the incorporation of a desired chemical moiety or a cleavable triggering unit into the compound in terms of, for example, chemical compatibility and/or steric considerations. Thus, for example, the incorporation of a spacer can provide one or more functional groups that enable to attach a cleavable triggering unit or a releasable unit to the polymeric backbone. The spacer can be further introduced to the polymer in order to enable the cross-linking between two polymers.

Being selected as self-immolative, the spacer participates in the self-immolative cascade disassembly reactions of the self-immolative polymers according to the present embodiments.

According to the present embodiments, the self-immolative spacer has a general formula selected from the group consisting of Formula Ha, Formula lib, Formula Hc, Formula Hd:

Formula Ha Formula lib

Formula He Formula Hd

and a combination thereof, wherein: d, e, f, g and h are each independently an integer from 0 to 3, provided that d + e + f

≥ 2;

R¹² and R¹³ are each independently hydrogen, alkyl or cycloalkyl; and

, 14 ,15 ,16

R'⁴, R¹⁰, R , R ₃1¹7', R^1B and R^ia are each independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate.

The self-immolative spacers presented by Formulae lla, lib, Hc and Hd above belong to the known ω-amino aminocarbonyl cyclization spacers, which undergo self-elimination via an intra-cyclization process so as to form urea derivatives, as exemplified in Figure 13 where such a spacer links between a releasable unit and the polymer's backbone. Such self- immolative linkers are therefore specifically advantageous in self-immolative polymers that are intended for biological and environmentally safe applications, as they result in biocompatible side products such as urea. This feature allows for a full biodegradation of the self-immolative polymers.

Furthermore, by being terminated with an amine group, such self-immolative spacers enable the formation of amide bonds, which, as is detailed herein and is further exemplified in the Examples section below, are preferable bonds in various embodiments of the present invention. Amide bonds are relatively stable under physiological conditions and hence, typically, do not undergo cleavage by background hydrolysis.

In addition, by selecting the chemical nature of the substituents on the alkylene chains which form a part of the self-immolative spacers (R¹²-R¹⁹ in Formulae lla-lld above), the hydrophobic/hydrophilic nature of the compound can be determined rendering either dissolvable or at least reasonably dissolvable in aqueous media (typically required for physiological and agricultural processes) or dissolvable or at least reasonably dissolvable in organic media (required for chemical reactions).

As is described hereinabove, the self-immolative spacers according to these embodiments can comprise any combination of the fragments presented in Formulae Ha, lib, Hc and Hd. The self-immolative spacers can further comprise or be interrupted with other units that self-immolate via the electronically-conjugated cascade self-elimination described hereinabove, as is detailed hereinunder.

The chemical characteristics and the length of the self-immolative spacers can be tailored according to specific requirements, needs and/or preferences. For example, in cases where the chemical moiety is a large, bulky molecule and the reaction between the cleavable triggering unit and the triggering factor requires unhindered cleavable triggering units (as in the case, for example, the triggering factor is an enzyme catalyzing the cleavage process), a long self-immolative spacer may be incorporated in the polymer, so as to avoid steric hindrance of the cleavable triggering unit and hence, the selected linker would comprise several, same or different, self-immolative linker units. Similarly, in cases where a releasable unit does not have a functionality which is compatible with the self-immolative system, such a seif-immolative spacer can be used to link between the polymer backbone and the releasable unit, thereby serving as an adaptor therebetween. Such an adaptation of a releasable unit is exemplified in the Examples section that follows below and illustrated in Figure 13. Thus, the self-immolative polymer described herein are comprised of a plurality of self-immolative building units, one or more cleavable triggering units, one or more releasable units, as described herein, and optionally one or more self-immolative spacers as described herein, linking between any of the units comprising the polymer, all are attached one to the other in accordance with the unique self-immolative system which can undergo a cascaded disassembly process. One of the criteria for selection of the various units of the polymer as presented herein, exhibiting suitable functionalities in accordance to the requirement for self-immolation is the capacity to form linking bonds that can participate in both the cleavage event(s) and the electronically-conjugated cascade of self-elimination reactions. Thus, for example, an amine group can form an amide bond, a carbamate bond, a thioamide bond, a thiocarbamate, an imine bond or an aza bond with a carboxylic-acid containing, a carbonate-containing, a thiocarboxylic acid-containing, a thiocarbonate-containing, an aldehyde-containing or an amine-containing cleavable triggering unit, respectively. Such bonds are typically stable under physiological conditions and therefore are not susceptible to biodegradation in the absence of a triggering event. Hence, such bonds are advantageous when the polymers are used in therapeutic or diagnostic applications.

As used herein the phrase "amide bond" refers to a -NR'-C(=O)- bond, where R' is hydrogen, alkyl, cycloalkyl or aryl.

The phrase "carbamate bond" refers to a -NR'-C(=O)-O- bond, where R' is as defined herein.

The phrase "thioamide bond" refers to a -NR'-C(=S)- bond, where R; is as defined herein.

The phrase "thiocarbamate bond" refers to a -NR'-C(=S)-O- bond, a NR'C(=S)-S- bond or a NR'C(=O)-S- bond. The phrase "imine bond", also known as Schiff base, refers to a -NR'=CR"- bond, where R' is as defined herein and R" is as defined for R'. The term "aza" bond refers to a -N=N- bond.

As used herein throughout, the term "alkyl" refers to a saturated aliphatic hydrocarbon including straight chain and/or branched chain groups. Preferably, the alkyl group is a medium size alkyl having 1 to 10 carbon atoms. More preferably, it is a lower alkyl having 1 to 6 carbon atoms. Most preferably it is an alkyl having 1 to 4 carbon atoms. Representative examples of an alkyl group are methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, pentyl and hexyl.

As used herein, the term "cycloalkyl" refers to an all-carbon monocyclic or fused ring (i.e., rings which share an adjacent pair of carbon atoms) group wherein one of more of the rings does not have a completely conjugated pi-electron system. Examples, without limitation, of cycloalkyl groups are cyclopropane, cyclobutane, cyclopentane, cyclopentene, cyclohexane, cyclohexadiene, cycloheptane, cycloheptatriene and adamantane.

The term "aryl" refers to an all-carbon monocyclic or fused-ring polycyclic (i.e., rings which share adjacent pairs of carbon atoms) group having a completely conjugated pi- electron system. Examples, without limitation, of aryl groups are phenyl, naphthalenyl and anthracenyl.

The term "heteroaryl" includes a monocyclic or fused ring (i.e., rings which share an adjacent pair of atoms) group having in the ring(s) one or more atoms, such as, for example, nitrogen, oxygen and sulfur and, in addition, having a completely conjugated pi-electron system. Examples, without iimitation, of heteroaryl groups include pyrrole, furane, thiophene, imidazole, oxazole, thiazole, pyrazole, pyridine, pyrimidine, quinoline, isoquinoline and purine.

The term "heterocycloalkyl" refers to a monocyclic or fused ring group having in the ring(s) one or more atoms such as nitrogen, oxygen and sulfur. The rings may also have one or more double bonds. However, the rings do not have a completely conjugated pi-electron system.

Each of the alkyls, cycloalkyl, aryls, heteroaryls and heterocycloalkyls described herein can be further substituted. When substituted, the substituent group may be, for example, halogen, alkyl, alkoxy, nitro, cyano, trihalomethyl, alkylamino or monocyclic heteroaryl.

As used herein, the term "hydroxy" refers to an -OH group.

The term "thiohydroxy" refers to a -SH group.

The term "alkoxy" refers to both an -O-alkyl and an -O-cycloalkyl group, as defined hereinbelow. Representative examples of alkoxy groups include methoxy, ethoxy, propoxy and tert-butoxy.

The term "thioalkoxy" refers to both a -S-alkyl and a -S-cycloalkyl group, as defined hereinabove.

The term "aryloxy" refers to both an -O-aryl and an -O-heteroaryl group, as defined herein. A "thioaryloxy" group refers to both an -S-aryl and an -S-heteroaryl group, as defined herein.

As used herein, the term "halo" refers to a fluorine, chlorine, bromine or iodine atom.

The term "trihalomethyl" refers to. a -CX₃ group, wherein X is halo as defined herein. A representative example of a trihalomethyl group is a -CF₃ group. The term "amino" or "amine" refers to an -NR¹R" group, where R' and R" are each independently hydrogen, alkyl or cycloalkyl, as is defined hereinabove.

The term "cyclic alkylamino" refers to an -NR'R" group where R' and R" form a cycloalkyl.

The term "nitro" refers to a -NO₂ group. The term "cyano" or "nitrile" refers to a -C≡N group.

The term "C-amido" refers to a -C(=O)-NR'R" group, where R' and R" are as described hereinabove.

The term "N-amido" refers to a -NR'-C(=O)-R", where R' and R" are as described hereinabove. The term "carboxylic acid" refers to a -C(=O)-OH group.

The term "carboxylate" refers to a -C(=O)-OR' group, where R' is as defined hereinabove.

The term "carbonate" refers to a -O-C(=O)-OR' group, where R' is as defined herein. The term "sulfate" refers to a "-S(=0)₂0R' group, where R' is as defined hereinabove.

The term "sulfonyl" refers to an -S(=O)₂-R' group, where R' is as defined herein.

The term "sulfinyl" refers to an -S(=O)R' group, where R' is as defined hereinabove. The term "phosphonate" refers to a -P(=O)(OH)₂ group.

The term "phosphate" refers to an -O-P(=O)(OR')(OR") group, where R' and R" are as defined hereinabove.

The building units presented hereinabove in Formulae Ia and Ib can be represented by alternative formulae, denoted Formula Ia' and Formula Ib¹, which differ from Formulae Ia and Ib by the way the repeating units are defined in terms of the "head" and "tail" moieties.

Thus, the present building units can be represented also by Formula Ia' and Formula Ib' as follows:

Formula Ia' Formula Ib' wherein:

V is O, S, PR⁶ or NR⁷;

U is O, S or NR⁸;

A, B, D and E are each independently a carbon atom or a nitrogen atom;

R¹, R², R³, R⁴ and R⁵ are each independently

, hydrogen, alky], aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, or alternatively, at least two of R¹, R², R³, R⁴ and R⁵ being connected to one another to form an aromatic or aliphatic cyclic structure; whereas: a, b and c are each independently as integer of 0 to 5; K is O, S, PR⁶ or NR⁷; and I₁ F and G are each independently -R¹¹C=CR¹²- or -C≡C-, where each of R¹¹ and R¹² is independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano,

C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, or, alternatively, R¹¹ and R¹² being connected to one another to form an aromatic or aliphatic cyclic structure; and

R⁶, R⁷ and R^s are each independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, provided that at least one of R¹-R³ in Formula Ia' and of R¹-R⁵ in Formula Ib' is the

The polymers described herein can be represented by a general formula selected from the group consisting of:

Q - A1 - [X-Y]n -A2 - W Q - A1 - [X(W)m-Y]n-1 - Xn

Formula IHa Formula UIb

wherein: n is an integer from 2 to 100; m is an integer from 1 to 4; Q is said cleavable triggering unit;

A1 and A2 are each independently said self-immolative spacer or absent; X is said building unit; Y is said self-immolative spacer or absent; and

W is said releasable unit.

As discussed hereinabove, the self-immolative polymers presented herein are designed so as to release upon the occurrence of a triggering event, a releasable unit, and preferably a plurality of releasable units. Representative examples of releasable units that can be beneficially incorporated in the self-immolative polymers described herein include, without limitation, therapeutically active agents, detectable agents, chemical reagents, agrochemicais and a building unit.

It would be appreciated that the phrases "therapeutically active agents, detectable agents, chemical reagents, agrochemicais and a building unit", when used to describe the releasable chemical moiety, refer to both a moiety thereof when incorporated into the self- immolative polymer and to the compound itself when released from the self-immolative polymer. These terms and phrases are also defined and exemplified hereinbelow.

Representative examples of therapeutically active agents that can be beneficially incorporated in the self-immolative polymer described herein include, without limitation, chemotherapeutic agents, anti-proliferative agents, anti-inflammatory agents, antimicrobial agents, anti-hypertensive agents, statins, psychotropic agents, anti-coagulants, anti-diabetic agents, vasodilating agents, analgesics, hormones, vitamins, metabolites, carbohydrates, peptides, proteins, amino acids, co-enzymes, growth factors, prostaglandins, oligonucleotides, nucleic acids, antisenses, antibodies, antigens, immunoglobulins, cytokines, cardiovascular agents, phospholipids, fatty acids, betacarotenes, nicotine, nicotinamide, antihistamines and antioxidants.

Non-limiting examples of anti-inflammatory agents useful in the context of the present embodiments include non-steroidal anti-inflammatory agents such as, for example, aspirin, celecoxib, diclofenac, diflunisal, etodolac, fenoprofen, flurbiprofen, ibuprofen, indomethacin, ketoprofen, ketorolac, meclofenamate, mefenamic acid, nabumetone, naproxen, oxaprozin, oxyphenbutazone, phenylbutazone, piroxicam, rofecoxib sulindac and tolmetin; and steroidal anti-inflammatory agents such as, for example, corticosteroids such as hydrocortisone, hydroxyltriamcinolone, alpha-methyl dexamethasone, dexamethasone-phosphate, beclomethasone dipropionates, clobetasol valerate, desonide, desoxymethasone, desoxycorticosterone acetate, dexamethasone, dichlorisone, diflorasone diacetate, diflucortolone valerate, fluadrenolone, fluclorolone acetonide, fludrocortisone, flumethasone pivalate, fluo^'sinolone acetonide, fluocinonide, flucortine butylesters, fluocortolone, fluprednidene (fiuprednylidene) acetate, flurandrenolone, halcinonide, hydrocortisone acetate, hydrocortisone butyrate, methylprednisolone, triamcinolone acetonide, cortisone, cortodoxone, flucetonide, fludrocortisone, difluorosone diacetate, fluradrenolone, fludrocortisone, diflurosone diacetate, fluradrenolone acetonide, medrysone, amcinafel, amcinafide, betamethasone and the balance of its esters, chloroprednisone, chlorprednisone acetate, clocortelone, clescinolone, dichlorisone, diflurprednate, flucloronide, flunisolide, fluoromethalone, fluperolone, fluprednisolone, hydrocortisone valerate, hydrocortisone cyclopentylpropionate, hydrocortamate, meprednisone, paramethasone, prednisolone, prednisone, beclomethasone dipropionate, triamcinolone, and mixtures thereof.

Non-limiting examples of psychotropic agents that can be beneficially incorporated in the self-immolative polymers described herein include antipsychotic agents, including typical and atypical psychotic agents, anti-depressants, mood stabilizers, anti-convulsants, anti- anxiolitics, anti-parkinsonian drugs, acetylcholine esterase inhibitors, MAO inhibitors, phenothiazines, benzodiazepines and butyrophenones.

Non-limiting examples of cardiovascular agents that can be beneficially incorporated in the self-immolative polymers described herein include alpha-adrenergic blocking drugs (such as doxazocin, prazocin or terazosin); angiotensin-converting enzyme inhibitors (such as captopril, enalapril, or lisinopril); antiarrhythmic drugs (such as amiodarone); anticoagulants, antiplatelets or thrombolytics (such as aspirin); beta-adrenergic blocking drugs (such as acebutolol, atenolol, metoprolol, nadolol, pindolol or propanolol); calcium channel blockers (such as diltiazem, nicardipine, verapamil or nimopidipine); centrally acting drugs (such as clonidine, guanfacine or methyldopa); digitalis drugs (such as digoxin); diuretics (such as chlorthalidone); nitrates (such as nitroglycerin); peripheral adrenergic antagonists (such as reserpine); and vasodilators (such as hydralazine).

Non-limiting examples of metabolites that can be beneficially incorporated in the self- immolative polymers described herein include glucose, urea, ammonia, tartarate, salicylate, succinate, citrate, nicotinate etc. Representative examples of commonly prescribed statins include Atorvastatin,

Fluvastatin, Lovastatin, Pravastatin and Simvastatin.

Non-limiting examples of analgesics (pain relievers) include non-narcotic analgesics such as aspirin and other salicylates (such as choline or magnesium salicylate), ibuprofen, ketoprofen, naproxen sodium, and acetaminophen and narcotic analgesics such as morphine, codaine, hydrocodone, hydromorphone, levorphanol, oxycodone, oxymorphone, naloxone, naltrexone, alfentanil, buprenorphine, butorphanol, dezocine, fentanyl, meperidine, methadone, nalbufine, pentazocine, propoxyphene, sufentanil, and tramadol.

Non-limiting examples of growth factors include insulin-like growth factor-1 (IGF-1), ^■ transfΘrmifig-growth-factor--β-(TGF-β)7-a-bone-morphogenic-protein tBMP) Bπd^"1he like: Non-limiting examples of toxins include the cholera toxin.

Non-limiting examples of anti-coagulants agents that can be beneficially incorporated in the self-immolative polymers described herein include dipyridamole, tirofiban, aspirin, heparin, heparin derivatives, urokinase, rapamycin, PPACK (dextrophenylalanine proline arginine chloromethylketone), probucol, and verapamil. Non-limiting examples of chemotherapeutic agents that can be beneficially incorporated in the self-immolative polymers described herein include amino containing chemotherapeutic agents such as daunorubicin, doxorubicin, N-(5,5- diacetoxypentyl)doxorubicin, anthracycline, mitomycin C, mitomycin A, 9-amino camptothecin, aminopertin, antinomycin, N⁸-acetyl spermidine, 1-(2-chIoroethyl)-1,2~dimethanesulfonyl hydrazine, bleomycin, tallysomucin, and derivatives thereof; hydroxy containing chemotherapeutic agents such as etoposide, camptothecin, irinotecaan, topotecan, 9-amino camptothecin, paclitaxel, docetaxel, esperamycin, 1 ,8-dihydroxy-bicyclo[7.3.1]trideca-4-ene- 2,6-diyne-13-one, anguidine, morpholino-doxorubicin, vincristine and vinblastine, and derivatives thereof, sulfhydril containing chemotherapeutic agents, carboxyl containing chemotherapeutic agents, platinum complexes, antibiotics and 5-FU and more.

Non-limiting examples of antimicrobial agents that can be beneficially incorporated in the self-immolative polymers described herein include antibiotics, anti-viral agents, anti-fungal agents, including, for example, iodine, chlorhexidene, bronopol, triclosan, famciclovir, valaciclovir, acyclovir, and derivatives thereof, penicillin-V, azlocillin, and tetracyclines, and derivatives thereof, neamine, neomycin, paramomycin, gentamycin, and derivatives thereof.

Non-limiting examples of vitamins that can be beneficially incorporated in the self- immolative polymers described herein include vitamin A₁ thiamin, vitamin B₆, vitamin B₁₂, vitamin C, vitamin D, vitamin E, vitamin K, riboflavin, niacin, folate, biotin and pantothenic acid.

Non-limiting examples of anti-diabitic agents that can be beneficially incorporated in the self-immolative polymers described herein include lipoic acid, acarbose, acetohexamide, chlorpropamide, glimepiride, glipizide, glyburide, meglitol, metformin, miglitol, nateglinide, pioglitazone, repaglinide, rosiglitazone, tolazamide, tolbutamide and troglitazone.

Non-limiting examples of antioxidants that are usable in the context of the present embodiments include ascorbic acid (vitamin C) and its salts, ascorbyl esters of fatty acids, ascorbic acid derivatives (e.g., magnesium ascorbyl phosphate, sodium ascorbyl phosphate, ascorbyl sorbate), tocopherol (vitamin E), tocopherol sorbate, tocopherol acetate, other esters of tocopherol, butylated hydroxy benzoic acids and their salts, 6-hydroxy-2, 5,7,8- tetramethylchroman-2-carboxylic acid (commercially available under the trade name Trolox^R), gallic acid and its alky! esters, especially propyl gallate, uric acid and its salts and alkyl esters, sorbic acid and its salts, lipoic acid, amines (e.g., N,N-diethylhydroxyiamine, amino- guanidine), sulfhydryl compounds (e.g., glutathione), dihydroxy fumaric acid and its salts, lycine pidolate, arginine pilolate, nordihydroguaiaretic acid, bioflavonoids, curcumin, lysine, methionine, proline, superoxide dismutase, silymarin, tea extracts, grape skin/seed extracts, melanin, and rosemary extracts.

Non-limiting examples of antihistamines usable in the context of the present embodiments include chlorpheniramine, brompheniramine, dexchlorpheniramine, tripolidine, clemastine, diphenhydramine, promethazine, piperazines, piperidines, astemizole, loratadine and terfenadine.

Suitable hormones for use in the context of the present embodiments include, for example, androgenic compounds and progestin compounds.

Representative examples of androgenic compounds include, without limitation, methyltestosterone, androsterone, androsterone acetate, androsterone propionate, androsterone benzoate, androsteronediol, androsteronediol-3-acetate, androsteronediol-17- acetate, androsteronediol 3-17-diacetate, androsteronediol-17-benzoate, androsteronedione, androstenedione, androstenediol, dehydroepiandrosterone, sodium dehydroeptandrosterone sulfate, dromostanolone, dromostanolone propionate, ethylestrenol, fluoxymesterone, nandrolone phenpropionate, nandrolone decanoate, nandrolone furylpropionate, nandrolone cyclohexane-propionate, nandrolone benzoate, nandrolone cyclohexanecarboxylate, androsteronediol-3-acetate-1-7-benzoate, oxandrolone, oxymetholone, stanozolol, testosterone, testosterone decanoate, 4-dihydrotestosterone, 5α-dihydrotestosterone, testolactone, 1/α-methyI-i 9-nortestosterone and pharmaceutically acceptable esters and salts thereof, and combinations of any of the foregoing.

Representative examples of progestin compounds include, without limitation, desogestrel, dydrogesterone, ethynodiol diacetate, medroxyprogesterone, levonorgestrel, medroxyprogesterone acetate, hydroxyprogesterone caproate, norethindrone, norethindrone acetate, norethynodrel, allylestrenol, 19-nortestosterone, lynoestrenol, quingestanol acetate, medrogestone, norgestrienone, dimethisterone, ethisterone, cyproterone acetate, chlormadinone acetate, megestrol acetate, norgestimate, norgestrel, desogrestrel, trimegestone, gestodene, nomegestrol acetate, progesterone, 5α-pregnan-3β,20α-diol sulfate, 5α-pregnan-3β,20β-diol sulfate, 5α-pregnan-3β-ol-20-one, 16,5α-pregnen-3β-ol-20- one, 4-pregnen-20β-ol-3-one-20-suifate, acetoxypregnenolone, anagestone acetate, cyproterone, dihydrogesterone, flurogestone acetate, gestadene, hydroxyprogesterone acetate, hydroxymethylprogesterone, hydroxymethyl progesterone acetate, 3- ketodesogestrel, megestrol, melengestrol acetate, norethisterone and mixtures thereof. Biomolecules that can be beneficially incorporated in the self-immolative polymers described herein, such as peptides, proteins, nucleic acids, oligonucleotides and antisenses are preferably selected such that they remain intact in the body when incorporated in the self- immolative polymers and exhibit a therapeutic activity upon their release.

Representative examples include, without limitation, relatively short peptides having up to 20 amino acid residues, antibody fragments, and relatively short oligonucleotides such as, for example, siRNA, and antisenses.

As is discussed hereinabove, utilizing self-immolative polymers as anti-proliferative prodrugs is highly beneficial due to the EPR effect. Hence, preferred therapeutically active agents according to the present invention include anti-proliferative agents such as chemotherapeutic agents.

As used herein, the phrase "detectable agent", describes an agent or a moiety that exhibits a measurable feature. This phrase encompasses the phrase "diagnostic agent", which describes an agent that upon administration exhibits a measurable feature that corresponds to a certain medical condition. Such agents and moieties include, for example, labeling compounds or moieties, as is detailed hereinunder.

Representative examples of detectable agents that can be beneficially incorporated in the self-immolative polymers described herein include, without limitation, signal generator agents and signal absorber agents.

As used herein, the phrase "signal generator agent" includes any agent that results in a detectable and measurable perturbation of the system due to its presence. In other words, a signal generator agent is an entity which emits a detectable amount of energy in the form of electromagnetic radiation (such as X-rays, ultraviolet (UV) radiation, infrared (IR) radiation and the like) or matter, and includes, for example, phosphorescent and fluorescent (fluorogenic) entities, gamma and X-ray emitters, (such as neutrons, positrons, β-particles, α- particles, and the like), radionuclides, and nucleotides, toxins or drugs labeled with one or more of any of the above, and paramagnetic or magnetic entities.

As used herein, the phrase "signal absorber agent" describes an entity which absorbs a detectable amount of energy in the form of electromagnetic radiation or matter. Representative examples of signal absorber agents include, without limitation, dyes, contrast agents, electron beam specifies, aromatic UV absorber, and boron (which absorbs neutrons).

As used herein, the phrase "labeling compound or moiety" describes a detectable moiety or a probe which can be identified and traced by a detector using known techniques such as spectral measurements (e.g., fluorescence, phosphorescence), electron microscopy, X-ray diffraction and imaging, positron emission tomography (PET), single photon emission computed tomography (SPECT), magnetic resonance imaging (MRi), computed tomography (CT) and the like.

Representative examples of labeling compounds or moieties include, without limitation, chromophores, fluorescent compounds or moieties, phosphorescent compounds or moieties, contrast agents, radioactive agents, magnetic compounds or moieties (e.g., diamagnetic, paramagnetic and ferromagnetic materials), and heavy metal clusters, as is further detailed hereinbelow, as well as any other known detectable moieties.

As used herein, the term "chromophore" refers to a chemical moiety or compound that when attached to a substance renders the latter colored and thus visible when various spectrophotometric measurements are applied.

A heavy metal cluster can be, for example, a cluster of gold atoms used, for example, for labeling in electron microscopy or X-ray imaging techniques.

As used herein, the phrase "fluorescent compound or moiety" refers to a compound or moiety that emits light at a specific wavelength during exposure to radiation from an external source.

As used herein, the phrase "phosphorescent compound or moiety" refers to a compound or moiety that emits light without appreciable heat or external excitation, as occurs for example during the slow oxidation of phosphorous. As used herein, the phrase "radioactive compound or moiety" encompasses any chemical compound or moiety that includes one or more radioactive isotopes. A radioactive isotope is an element which emits radiation. Examples include α-radiation emitters, β- radiation emitters or γ-radiation emitters.

Representative examples of agrochemicals that can be beneficially incorporated as releasable chemical moieties in the self-immolative polymers described herein include, without limitation, fertilizers, such as acid phosphates and sulfates; insecticides such as chlorinated hydrocarbons (such as p-dichlorobenzene), imidazoles, and pyrethrins, including natural pyrethrins; herbicides, such as carbamates, derivatives of phenol and derivatives of urea; and pheromones. In one preferred embodiment of the present invention, the releasable unit is by itself a self-immolative system, referred to herein as a second self-immolative compound.

The phrase "second seif-immolative compound" as used herein, refers to a -self- immolative polymer as presented and described herein as well as to any other self-immolative compound which comprises a plurality of building units optionally connected via one or more self-immolative spacers, and having one or more cleavable triggering units and at least one releasable units, as these terms are defined herein. Preferably, the phrase "second self- immolative compound" encompasses a self-immolative compound which is designed such that upon cleavage of one or more of the cleavable triggering units on either the second self- immolative compound itself or the self-immolative polymer it is attached to, the tail releasable units thereof are released. One particular example of such second self-immolative compound can be any of the self-immolative dendritic compounds or dendrimers as taught in WO 2004/019993, U.S. Patent Application No. 2005/0271615 and/or U.S. Patent Application No. 2006/0269480, which are incorporated herein by reference as if fully set forth herein. Further according to the present invention there is provided a process of preparing a self-immolative polymer as described herein, the process is effected by: polymerizing a plurality of building units, attaching at least one releasable unit to at least one of the building units, and attaching at least one cleavable triggering unit to the polymeric backbone. Alternatively the cleavable triggering unit(s) is attached to the polymeric backbone prior to attaching the releasable unit(s)

Figure 1 presents a schematic illustration of a general procedure, according to embodiments of this aspect of the present invention, by which an exemplary self-immolative linear polymer having a cleavable triggering unit and a releasable unit (denoted "reporter"), is prepared.

As can be seen in Figure 1, self-immolative linear polymers can be prepared by simple polymerization of a bifunctional molecule (building unit), wherein "H" denotes a "head" functional group and "T" denotes a "tail" functional group. When a monomer "T-H" is subjected to appropriate polymerization conditions, the corresponding linear polymer is formed. Subsequent capping of the terminal head group with a specific protecting group (a cleavable triggering unit) will generate a stable polymer molecule, namely protected from spontaneous self-immolative disassembly. Finally, a reporter group (releasable unit) can be attached to the terminal tail. Selective cleavage of the cleavable triggering unit will initiate the domino-like fragmentation of the polymer in a self-immolative manner, leading to the release of the terminal reporter molecule, as exemplified in the Examples section that follows below.

This, general procedure for preparing a simple self-immolative linear polymer is further exemplified in Figures 5a-b which present a chemical scheme of the synthesis of an exemplary self-immolative polymer having a cleavable triggering unit, Compound 1 (Figure 5a), and the chemical scheme of the synthesis of the corresponding monomer precursor, Compound 5 (Figure 5b). This exemplary process is further discussed in the Examples section that follows.

According to some embodiments of this aspect of the present invention, at least one of the building units is having at least one releasable unit attached thereto prior to the polymerization process. In some of these embodiments the building unit(s) which comprises the polymer is also referred to hereinabove as an AB₃ unit, having one "head" and three "tails" (see, for example, U.S. Patent Application No. 2005/0271615). In these embodiments resulting polymer will have releasable units attached to the polymeric backbone ialong the polymer, resulting in a polymer which can be referred to as a comb polymer. Figure 2 presents a schematic illustration of a general procedure, according to these embodiments, by which this form of a self-immoiative polymer, i.e. a self-immolative comb polymer having a cleavable triggering unit and a plurality of releasable units (marked by an R in a red circle), is prepared. This concept is also depicted in Figure 7, while a different synthetic approach is depicted in Figure 9, wherein the polymer's backbone is first constructed and then the releasable units are attached thereto.

As can be seen in Figures 2, 7, 9 and 12, comb-shaped self-immolative polymers are macromolecules of central elongated backbone with side groups pointing out in a repetitive and ordered fashion. As can be seen in Figure 2, a head-tail monomer with two side reporter (R) groups, or releasable units, can be polymerized and then capped with a cleavable triggering unit to form a self-immolative comb polymer. As can be seen in Figure 12, selective cleavage of the cleavable triggering unit will initiates a self-immolative fragmentation of the polymer and the release of the side reporter units. This exemplary process is further discussed in the Examples section that follows.

According to other embodiments of this aspect of the present invention, at least one of the building units is having at least one other building unit attached thereto prior to the polymerization process. The use of this type of branching building unit results in a branched polymer.

According to further embodiments, the branches on the branching building unit are each having releasable unit(s) attached thereto prior to the polymerization process. Figure 3 presents a schematic illustration of an exemplary self-immolative branched polymer according to embodiments of this aspect of the present invention, having a cleavable triggering unit and a backbone of repetitive branching units, each carrying at least two releasable units or reporter groups. Similar polymers are presented in Figures 10 and 11. In principle, the releasable units on the monomer of a comb polymer, presented hereinabove, can be replaced by a self-immolative unit, each carrying a multi-number of releasable units. A non-limiting example of such a unit is referred to hereinabove as an AB₃ unit, having one "head" and three "tails" (see, for example, U.S. Patent Application No. 2005/0271615). As can be seen in Figures 3, 10 and 11 , polymerization of such monomers will form a self- immolative branched polymer, which is then capped with a cleavable triggering unit. Cleavage of the triggering unit would initiate a self-immolative fragmentation of the polymer along the backbone, and the release of the side self-immoiative branching units and the overall release of the releasable units attached thereto. This exemplary process is further discussed in the Examples section that follows.

The above described self-immolative polymeric systems can be utilized in variety of applications, particularly where molecular delivery vehicles and molecular signal amplifications systems are required.

Each of the self-immolative polymers described herein can be specifically designed, by selecting the appropriate bonds between the units, to be completely stable prior to being subjected to a triggering event . The self-immolative polymers may be further designed to self-immolate in a particular environment and conditions, such as in an aqueous medium, a feature that is highly advantageous in many of the applications that utilize these self- immolative polymers beneficially. Moreover, the self-immolative polymers presented herein can be designed to disassemble as an AND or OR logic gate, as discussed hereinabove, and carry particular triggering units so as to render them highly specific and targeted to a pre- determined biological, physiological or chemical environments. This particular trait is highly beneficial in therapeutic and in-vivo diagnosis applications.

As is exemplified in the Examples section that follows, while reducing the present invention to practice, self-immolative polymers as described hereinabove, having various triggering units and various releasable chemical moieties have been synthesized and successfully tested for their capability to release the chemical moiety upon a pre-determined triggering mechanism, thus demonstrating the versatility of the self-immolative polymers of the present invention, as is described hereinbelow.

As discussed herein, the self-immolative polymers can be utilized as efficient prodrug or drug delivery vehicles. Incorporation of drug molecules as releasable units in a comb-type or branched-type self-immolative polymers will generate a prodrug polymeric system with high payload. Specific removal of the trigger will release all the drug units selectively at the predetermined target/site. For example, a self-immolative polymer according to the present embodiments can comprise one or more biocleavable (e.g., enzymatically cleavable) triggering units and a plurality of therapeutically active agent units as releasable units, and therefore can serve as a highly efficient prodrug, as illustrated in Figure 12 and further discussed and exemplified in the Examples section that follows.

One important application for these prodrug polymers as a drug delivery system will be the release of a high concentration of an active chemotherapeutic drug for tumor treatment. These drug-carrier units might offer new solutions for obstacles like insufficient prodrug activation at the tumor site, especially in cases where MDR sets in.

Another important use for these self-immolative polymers could be applied in the field of diagnostics. The self-immolative polymeric molecules could be used for amplification of diagnostic signals generated by an enzyme, a chemical reagent or radiation, depending on the applied trigger and triggering unit. The releasable units of the polymer will be released through a single triggering event and as an enzymatic or chemical cleavage. For example, a fluorogenic molecule, as an exemplary detectable agent, that generates an active signal upon its release can be used as a releasable unit. Since the self- immolative polymeric system can carry multiple numbers of fluorogenic molecules, the signal generated upon cleavage of the trigger will be amplified significantly. Various protecting groups can be used as triggering units. These triggering units can be selected or designed for removal by enzymes, chemical reagents or photochemical reactions and events.

The self-immolative polymers can also be used in agricultural applications. For example, a pesticide agent can by used as a releasable unit and removal of a hydrolyzable triggering unit will release all the pesticide units selectively at the desired agricultural target or site. In another example, a self-immolative polymer according to the present embodiments comprises one or more hydrolizable triggering units and a fertilizing agent as a releasable unit can serve as an efficient plat growth booster in many plant nutrition compositions.

The self-immolative polymers can also be used in the manufacturing of many articles of daily use. Plastic products such as cutlery, bottles and nylon bags, and other disposable and non-degradable products, are one of the main causes for persistent environment pollution. Self-immolative polymers could serve as partial or complete replacements for the polymers used today to manufacture all the products with specific degradable qualities. For example, polyurethanes are used currently as absorbents in diapers, and hence disposable diapers are known as a serious polluting factor which attracts many research efforts to develop recyclable disposable diapers. Self-immolative polyurethane polymers can provide an efficient solution to this problem.

Many polyurethane-based polymers are known as biocompatible and are used in many medical applications (such as implants). Evidently, the self-immolative polymers presented herein can be designed to be both biocompatible and biodegradable. As such, the self-immolative polymers presented herein can be used for forming fibers and films for the manufacturing of many plastic-based articles used in agriculture, storage and container vessels, fishing, and more preferably in the construction of medical devices, such as controlled biodegradable fibers and implantable devices and the likes.

The rate of the self immolative polymer degradation can be controlled by synthetic modifications in order to provide the required qualities for the product. Time lengths for degradation could last from seconds to months in a controlled manner.

Thus, the self-immolative polymers described herein can be used for the construction of chemical linkers or polymeric cross-linking agents with controlled time delay of "detonation", depending on the polymer molecule length. These polymers may also be used for the preparation of simply degradable polymeric material with a controlled initiation.

As discussed herein, the self-immolative polymers according to the present embodiments can be used as delivery systems for therapeutic agents. Thus, according to another aspect of the present invention there is provided a method of treating a medical condition in a subject, which is effected by administering to the subject a therapeutically effective amount of a self-immolative polymer that comprises one or more therapeutically active agents as a releasable unit, or tail units. The polymer utilized in this method comprises a therapeutically active agent that can be beneficially used for treating the medical condition.

Alternatively, according to another aspect of the present invention, there is provided a use of an effective amount of a self-immolative polymer that comprises one or more therapeutically active agents as a releasable unit, or tail units, for the treatment of a medical condition in a subject.

Preferably, the self-immolative polymer utilized in this method or use further comprises an enzymatically cleavable triggering unit.

The term "administering" as used herein refers to a method for bringing a self- immolative polymer of the present invention into an area or a site in the subject that is impaired by the disorder or disease.

The term "therapeutically effective amount" refers to that amount of the self- immolative polymer being administered which will relieve to some extent one or more of the symptoms of the disorder or disease being treated. Representative examples of medical conditions that are treatable by the method according to this aspect of the present invention include, without limitation, the following:

Allergic diseases such as asthma, hives, urticaria, a pollen allergy, a dust mite - allergy, a venom allergy, a cosmetics allergy, a latex allergy, a chemical allergy, a drug allergy, an insect bite allergy, an animal dander allergy, a stinging plant allergy, a poison ivy allergy, anaphylactic shock, anaphylaxis, and a food allergy;

Cardiovascular diseases such as occlusive disease, atherosclerosis, myocardial infarction, thrombosis, Wegener's granulomatosis, Takayasu's arteritis, Kawasaki syndrome, anti-factor VIlI autoimmune disease, necrotizing small vessel vasculitis, microscopic polyangiitis, Churg and Strauss syndrome, pauci-immune focal necrotizing glomerulonephritis, crescentic glomerulonephritis, antiphospholipid syndrome, antibody induced heart failure, thrombocytopenic purpura, autoimmune hemolytic anemia, cardiac autoimmunity, Chagas" disease, and anti-helper T lymphocyte autoimmunity;

Metabolic diseases such as pancreatic disease, Type I diabetes, thyroid disease, Graves' disease, thyroiditis, spontaneous autoimmune thyroiditis, Hashimoto's thyroiditis, idiopathic myxedema, ovarian autoimmunity, autoimmune anti-sperm infertility, autoimmune prostatitis and Type 1 autoimmune polyglandular syndrome;

Gastrointestinal diseases such as colitis, ileitis, Crohn's disease, chronic inflammatory intestinal disease, inflammatory bowel syndrome, chronic inflammatory bowel disease, celiac disease, an ulcer, a skin ulcer, a bed sore, a gastric ulcer, a peptic ulcer, a buccal ulcer, a nasopharyngeal ulcer, an esophageal ulcer, a duodenal ulcer and a gastrointestinal ulcer;

Respiratory diseases such as asthma, emphysema, chronic obstructive pulmonary disease and bronchitis;

CNS diseases such as multiple sclerosis, Alzheimer's disease, Parkinson's disease, epilepsy, myasthenia gravis, motor neuropathy, Guillain-Barre syndrome, autoimmune neuropathy, Lambert-Eaton myasthenic syndrome, paraneoplastic neurological disease, paraneoplastic cerebellar atrophy, non-paraneoplastic stiff man syndrome, progressive cerebellar atrophy, Rasmussen's encephalitis, amyotrophic lateral sclerosis, Sydeham chorea, Gilles de Ia Tourette syndrome, autoimmune polyendocrinopathy, dysimmune neuropathy, acquired neuromyotonia, arthrogryposis multiplex, optic neuritis, spongiform encephalopathy, migraine, headache, cluster headache, and stiff-man syndrome;

Psychiatric diseases such as psychotic diseases (e.g., paranoia, schizophrenia), anxiety, dissociative disorders, personality disorders, mood disorders, affective disorders, boarder line disorders and mental diseases; Autoimmune diseases such as autoimmune myositis, smooth muscle autoimmune disease, lupus erythematosus, arthritis, and rheumatoid arthritis;

Bacterial, viral and/or fungal diseases, including gangrene, sepsis, a prion disease, influenza, tuberculosis, malaria, acquired immunodeficiency syndrome, and severe acute respiratory syndrome; and Proliferative diseases or disorders such as cancer, including, for example, brain, ovarian, colon, prostate, kidney, bladder, breast, lung, oral and skin cancers, and, moer particularlym glioblastoma multiforme, anaplastic astrocytoma, astrocytoma, ependyoma, oligodendroglioma, meduiloblastoma, meningioma, sarcoma, hemangioblastoma, pineal parenchymal, adenocarcinoma, melanoma and Kaposi's sarcoma. In one embodiment, the medical condition is cancer and the polymer comprises, as a therapeutically active agent, a chemotherapeutic agent, either alone or in combination with a chemosensitizing agent.

As discussed herein, the self-immolative polymers according to the present embodiments can be used as diagnostic agents. Thus, according to yet another aspect of the present invention, there is provided a method of performing a diagnosis, which is effected by administering to a subject in need thereof a diagnostically effective amount of a polymer as described herein, which comprises one or more biocleavable triggering units (e.g., enzymatically cleavable triggering units) and one or more detectable agents as the releasable or tail units. Alternatively, according to another aspect of the present invention, there is provided a use of a diagnostically effective amount of a self-immolative polymer that comprises one or more biocleavable triggering and one or more detectable agents as the releasable or tail units, for performing a diagnosis in a subject.

The detectable agent is selected suitable for the technique used in the diagnosis, as is detailed hereinabove.

The phrase "a diagnostically effective amount" includes an amount of the agent that provides for a detectable and measurable amount of the energy emitted or absorbed thereby. The method according to this aspect of the present invention can therefore be utilized to perform diagnoses such as, for example, radioimaging, nuclear imaging, X-ray, PET, SPECT, CT, diagnoses that involve contrasts agents and the like, using the suitable detectable agent, as is detailed hereinabove.

A self-immolative polymer according to the present embodiments, which comprises enzymatically cleavable triggering units and a detectable agent, can further be utilized to quantitatively and/or qualitatively compare the catalytic activity of enzymes. Hence, according to yet another aspect of the present invention there is provided a method of determining a comparative catalytic activity of one or more enzymes. The method, according to this aspect of the present invention, is effected by utilizing a polymer, as described herein, which comprises one or more enzymatically cleavable triggering units, each being a substrate of a different enzyme, and a detectable agent as the releasable unit, and monitoring the rate of self-immolation induced by the enzyme or each of the enzymes (by measuring the kinetics of the signal generation) upon subjecting the polymer to a triggering event effected by the enzyme, or each of the enzymes. The comparative rates of signal generation for the enzyme, or each enzyme, are indicative for the comparative catalytic activity of the tested enzyme(s). This method can be effected in vitro, to thereby determine a comparative catalytic activity of enzymes in, for example, cells cultures or samples. The detectable agent in this case can be, for example, a fluorogenic agent that fluoresces or quenches upon release, such that the enzyme activity is determined by a simple fluorescence measurement. Alternatively, this method or use can be effected in vivo. Some of the methods and uses described above involve administration of the polymers described herein to a subject. The polymers used in these methods can be administered either perse, or preferably, be formulated in a pharmaceutical composition.

Hence, according to still another aspect of the present invention, there are provided pharmaceutical compositions, which comprise any of the polymers described above and a pharmaceutically acceptable carrier.

Depending on the selected components of the polymer, the pharmaceutical compositions of the present invention can be packaged in a packaging material and identified in print, in or on the packaging material, for use in the treatment of a medical condition, as described hereinabove, or for diagnosis, as described hereinabove. Alternatively, according to another aspect of the present invention there is provided a use of any of the polymers described herein in the preparation of a medicament useful in the treatment of a medical condition.

As used herein a "pharmaceutical composition" or "medicament" refers to a preparation of one or more of the polymers described herein, with other chemical components such as pharmaceutically suitable carriers and excipients. The purpose of a pharmaceutical composition is to facilitate administration of a compound to an organism.

Hereinafter, the term "pharmaceutically acceptable carrier" refers to a carrier or a diluent that does not cause significant irritation to an organism and does not abrogate the biological activity and properties of the administered compound. Examples, without limitations, of carriers are: propylene glycol, saline, emulsions and mixtures of organic solvents with water.

Herein the term "excipient" refers to an inert substance added to a pharmaceutical composition to further facilitate administration of a compound. Examples, without limitation, of excipients include calcium carbonate, calcium phosphate, various sugars and types of starch, cellulose derivatives, gelatin, vegetable oils and polyethylene glycols.

Techniques for formulation and administration of drugs may be found in "Remington's Pharmaceutical Sciences," Mack Publishing Co., Easton, PA, latest edition, which is incorporated herein by reference. The pharmaceutical compositions described herein can be formulated for various routes of administration. Suitable routes of administration may, for example, include oral, sublingual, inhalation, rectal, transmucosal, transdermal, intracavemosal, topical, intestinal or parenteral delivery, including intramuscular, subcutaneous and intramedullary injections as well as intrathecal, direct intraventricular, intravenous, intraperitoneal, intranasal, or intraocular injections.

Formulations for topical administration include but are not limited to lotions, ointments, gels, creams, suppositories, drops, liquids, sprays and powders. Conventional carriers, aqueous, powder or oily bases, thickeners and the like may be necessary or desirable. Compositions for oral administration include powders or granules, suspensions or solutions in water or non-aqueous media, sachets, capsules or tablets. Thickeners, diluents, flavorings, dispersing aids, emulsifiers or binders may be desirable.

Formulations for parenteral administration may include, but are not limited to, sterile solutions which may also contain buffers, diluents and other suitable additives. Slow release compositions are envisaged for treatment.

The compositions may, if desired, be presented in a pack or dispenser device, such as an FDA (the U.S. Food and Drug Administration) approved kit, which may contain the polymer. The pack may, for example, comprise metal or plastic foil, such as, but not limited to a blister pack or a pressurized container (for inhalation). The pack or dispenser device may be accompanied by instructions for administration. The pack or dispenser may also be accompanied by a notice associated with the container in a form prescribed by a governmental agency regulating the manufacture, use or sale of pharmaceuticals, which notice is reflective of approval by the agency of the form of the compositions for human or veterinary administration. Such notice, for example, may be of labeling approved by the U.S. Food and Drug Administration for prescription drugs or of an approved product insert.

Some of the building units that form the polymeric backbone described herein can further be used to form a polymer per se.

Thus, according to embodiments of the present invention, there is provided a polymer which includes a plurality of building units linked to one another, each of the building units independently having a general formula selected from the group consisting of. Formula Ia and Formula Ib, as described herein. Such polymers can further comprises one or more spacer(s), as described herein.

Such polymers can further comprise a cleavable triggering unit, as described herein.

Such polymers can be utilized as self-immolative polymers, which decompose into small fragments upon a triggering event, and hence can be beneficially utilized in the manufacture of various articles, as described herein.

Additional objects, advantages, and novel features of the present invention will become apparent to one ordinarily skilled in the art upon examination of the following examples, which are not intended to be limiting. Additionally, each of the various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below finds experimental support in the following examples.

EXAMPLES Reference is now made to the following examples, which together with the above descriptions, illustrate the invention in a non limiting fashion.

EXAMPLE 1 Synthesis of a polycarbamate-based self-immolative polymer An exemplary synthesis of a polycarbamate-based self-immolative polymer is illustrated in Scheme 1 below:

Scheme 1 DBTL 2.5 % mol

Toluene/110⁰C, 15 min

(4-ammophenyl)methano! phenyl 4-

(hydrαxymethyl)phenylcarbamate

4-Aminobenzyl alcohol (1.5 grams 12.18 mmol, 1 equivalent) was dissolved in a mixture of THF, water and saturated NaHCO₃ (10 ml, 2:1:2 respective ratio), and phenylchlorophormate (1.57 ml, 12.48 mmol, 1.025 equivalents) was slowly added thereto. The reaction was monitored to completion by TLC, extracted with EtOAc and the product purified by flash chromatography to give phenyl 4-(hydroxymethyl)phenylcarbamate (2.81 grams, 95 % yield).

¹H-NMR (200 MHz,. CDCI₃): δ = 7.36-7.1 (m, 9H), 6.88 (s, 1H), 4.60 (s, 2H). 4-(Hydroxymethyl)phenylcarbamate (150 mg, 0.62 mmol, 1 equivalent) was suspended in toluene and heated for 15 minutes at 110 ⁰C in the presence of DBTL (9 μl, 0.0155 mmol, 2.5 % mol) and under argon atmosphere. The reaction was then cooled to room temperature and the polymer was precipitated by the addition of MeOH. The suspension was filtered and the polymer was dried under reduced pressure for 24 hours. This exemplary carbamate-based polymer contained 15 monomeric building units and was obtained as a white powder (50-75 mg, 35-50 % yield).

¹H-NMR (200MHz, DMSO-d6): δ = 9.77 (s, 15H), 7.41 (d, J = 8.0Hz, 30H), 7.31 (d, J = 8.0Hz, 30H), 5.03 (s, 30H), 4.38 (d, J = 5.5Hz, 2H). Figures 5a-b present a schematic illustration of the preparation of another exemplary polycarbamate-based self-immolative polymer. Figure 5a presents the polymer fitted with a cleavable triggering unit, and Figure 5b presents the synthetic procedure for the preparation of the monomer precursor (Compound 5). As can be seen in Figure 5a, the polymeric backbone is synthesized by polymerization of 4-isocyanate-benzylalcohol (Compound 6), prepared in situ from 4-acylazide-benzylalcohol (Compound 5) to generate a polycarbamate (Compound 7). Since the terminal head group is isocyanate, a 1 ,6-elimination process cannot take place due to the electrons pair of the isocyanate nitrogen being delocalized by the CO electronegative group. Therefore the polymeric molecule is capped with a hydroxy- containing trigger to form stable carbamate linkage (Compound 1). As can further be seen in Figure 5b, the monomer precursor, Compound 5, is prepared from commercially available 4-hydroxybenzyl-benzoic acid (Compound 8). Dicyclohexylcarbodiimide (DCC) activation followed by /V-hydroxy succinimide (NHS) affords an active ester (Compound 9) that can react with sodium azide to generate Compound 5.

Briefly, the monomeric building unit (Compound 5) was prepared according to the general procedure illustrated in Figure 5a, as follows. The acylazide intermediate was heated to 80 ⁰C in DMF, affording the isocyanate Compound 6 via Curtis rearrangement. The latter was polymerized in situ to form corresponding oligomers. Addition of methanol to the reaction mixture generated the precipitation of the polymerized material. The precipitate was filtered, washed with methanol and analyzed by NMR and MS. The sample exhibited two different peaks the for the benzylic hydrogens in the NMR analysis; one was attributed to the benzyl-alcohol and the other is attributed to the benzyl- carbamate. The ratio between the two peaks indicated that in average the polymer is constructed from seven monomers units.

Figures 6a-b present the mass spectrum analysis of this exemplary self-immolative polymer (Figure 6a) and the chemical structures of the oligomers observed in the MS. As can be seen in Figure 6a, the MS results confirmed the assumption that the polymer is constructed from seven monomers units, showing the mass values for the expected oligomers (Figure 6b).

EXAMPLE 2

Disassembly mechanism of a polycarbamate-based self-immolative polymer

Figure 4a presents the disassembly mechanism of a polycarbamate-based self- immolative polymer.

An exemplary self-immolative polymer according to the present embodiments was based on Compound 1 (Figure 4a). Briefly, this polymer was constructed from a polycarbamate backbone with a protecting group on the terminal amine, which acts as the cleavable triggering unit (denoted "triggering unit"). Chemical cleavage of the protecting group generates the amine Compound 2 that undergoes spontaneous sequential 1,6- elimination and decarboxylation reactions to form carbon dioxide and azaquinone-methide Compound 3. When the disassembly takes place under aqueous conditions the highly reactive azaquinone-methide reacts with water to form stable 4-amino-benzylalcohol (Compound 4).

EXAMPLE 3 Synthesis of a polycarbonate-based self-immolative polymeric backbone

Based on the synthetic concept of the polycarbamate-based self-immolative polymers presented hereinabove, polycarbonate-based self-immolative polymers can be prepared.

Figure 4b presents the design and disassembly mechanism of a polycarbonate- based self-immolative polymer. As can be seen in Figure 4b the polymer backbone is constructed from polycarbonate (Figure 4b) or polyether.

EXAMPLE 4 Design and synthesis of a self-immolative comb polymeric backbone

Figure 3 presents a schematic illustration of an exemplary self-immolative comb polymer having a cleavable triggering unit and a backbone of repeating branching units, each carrying at least two releasable units or reporter groups.

Figure 7 presents the general synthesis of a self-immolative comb polymer having a cleavable triggering unit attached thereto. As can be seen in Figure 7, self-immolative comb polymeric backbone can be prepared, according to some embodiments of the present invention, by polymerization of isocyanate monomer (Compound 10). Capping of the resulting polymer with a cleavable triggering unit affords the exemplary self-immolative comb polymer, Compound 11. As discussed hereinabove, removal of cleavable triggering unit initiates the cascade fragmentation along the polymer backbone into small fragments. In addition, each fragment should further disassemble in a similar self-immolative manner to release the releasable units or reporter groups.

An exemplary procedure for preparing a comb polymer is provided hereinbelow. The preparation of one component of the monomeric building unit, Compound 106, on the route for the preparation of an exemplary comb polymer, was carried out as illustrated in Scheme 2 below: Scheme 2

The preparation of another component of the monomeric building unit, Compound 111, on the route for the preparation of an exemplary comb polymer, was carried out as illustrated in Scheme 3 below:

Scheme 3

The polymerization and subsequent deprotection of the comb polymer is illustrated in Scheme 4 below.

Scheme 4

113 114

Preparation of Compound 113: DBTDL (20 L, 25 mol) was added to a solution of Compound 112 (100 mg, 0.13 nnmol) in 250 I dry DMF. The solution was stirred for 15 minutes at 110 ⁰C, and thereafter neat 4-hydroxy-2-butanone (100 L, 1.12 mmol) was added thereto. The homogeneous solution was stirred for 15 additional minutes and then cooled to room temperature. Excess of MeOH was added and the white precipitate was filtered and dried to afford the polymer Compound 113 as a white solid (45 mg, 50 % yield). 1H NMR(200 MHz₁ CHCI₃): . J . s, 5H), 8.11 (d, J=4.4 Hz, 10H), 5.2 (s ,20H), 4.75

(d, J=3 Hz, 10H), 4.42 (d ,J=2.88 Hz, 2H), 4.20 (t, J=3 Hz 3H), 2.79 (t, 2H), 2.10 (s, 3H), 1.20 (s, 15H).

Preparation of Compound 114: The polymer Compound 113 was treated with a DCM/TFA (1:1) solution for 5 minutes. Solvent was removed under reduced pressure to obtain 40 mg of the final comb polymer Compound 114 as a yellowish oil (38 mg, 92 % yield). Removal to the t-butyl was verified by NMR by the disappearance of the peak in =2.10, while all the expected peaks of the polymer were observed.

Figure 8 presents a . schematic illustration of the disassembly mechanism of an exemplary self-immolative comb polymer according to embodiments of the present invention, Compound 12, constructed from repeating branching units, each having a "head" and three "tails", referred to herein by the general term "AB₃ unit" or "AB₃ monomer". The disassembly mechanism has been reported and demonstrated previously by the synthesis and activation of single triggered AB₃ unit prodrug [Sagi, A., Bioorg. Med. Chem., Volume 15, Issue 11 , pp. 3720-7]. As can be seen in Figure 8, the triple azaquinone-methide elimination mechanism is initiated by, for example, enzymatic cleavage of a substrate triggering unit. The cleavage of this substrate triggering unit on the AB₃ unit (Compound 12) releases three releasable units or reporter groups. Figure 9 presents a schematic illustration of the synthesis of another exemplary self- immolative comb polymer having a cleavable triggering unit according to embodiments of the present invention. The synthesis of this alternative yet similar self-immolative comb polymer starts with the polymerization of another type of an AB₃ unit, Compound 13 (see, Figure 9), and the subsequent attachment of releasable units or reporter groups thereto. The side hydroxyl groups on the AB₃ unit are. protected by protecting group, denoted by P in Figure 9, and therefore do not interrupt with the polymerization process. Deprotection of the resulting polymer (Compound 14) affords the free hydroxybenzyl groups, which are then reacted with p-nitrophenyl-chloroformate to generate the active carbonate.

Finally, releasable units or reporter groups exhibiting an amine functionality are attached to the polymer to form self-immolative comb polymer (Compound 15). This alternative synthesis can be applied when using reporter groups with functional groups that may react with the isocyanate and therefore, interfere with the polymerization reaction.

EXAMPLE 5 Design and synthesis of self-immolative branched polymers

Replacing the two releasable units or reporter groups of the monomer which is referred to herein as Compound 10 with two self-immolative branching units generates a new monomeric unit with the capacity to carry a plurality of reporter groups. This monomeric unit is then used to construct a self-immolative branched polymer. Figure 10 presents a schematic illustration of the preparation of an exemplary self- immolative branched polymer having a cleavable triggering unit according to embodiments of the present invention.

As can be seen in Figure 10, the incorporation of the previously described AB₃ unit to Compound 10 affords a monomer with six releasable units or reporter groups such as, for example, Compound 16. Polymerization of such a monomer and subsequent capping thereof with a cleavable triggering unit results in the formation of self-immolative branched polymer, Compound 17, which can release all its reporter units by a single cleavage event of the cleavable triggering unit.

Similarly to the synthesis of the comb polymers, the alternative synthesis could be applied in the preparation of the branched polymers. The AB₃ units with the releasable units or reporter groups can be attached to the polymer backbone the polymerization process, as presented in Figure 9. EXAMPLE 6

Preparation of self-immolative polymers with a detectable releasable group

One important application of the single-triggered polymeric systems described herein -is the amplification of signals for diagnosis. Figure 11 presents a schematic illustration of the activation and subsequent cascade break-down of an exemplary self-immolative branched polymer according to embodiments of the present invention (Compound 18), which releases a plurality of reporter groups, namely 5- amino-2-nitro-benzoic acid (Compound 19), after a triggering event effected by peniciliin-G- amidase (PGA) which cleaves off the cleavable triggering unit phenylacetamide (marked in red in Figure 11).

5-amino-2-nitro-benzoic acid (Compound 19) is a colorless molecule when the amine group is occupied in a carbamate or an amide group, namely, when the amine group is protected. This is the state of the amine group of Compound 19 when it is attached through a carbamate linkage to a self-immolative branched polymer, such as the exemplary polymer Compound 18, presented in Figure 11. In sharp contrast, Compound 19 has a distinct yellow color in its free amine form. As can be seen in Figure 11 , the triggering event, effected by the enzyme PGA, generates a colored and hence detectible species in the form of 5-amino-2- nitro-benzoic acid. The introduction of phenylacetamide as a cleavable triggering unit in the polymer Compound 18 generates a molecular sensor for the enzyme penicillin-G-amidase (PGA). A single cleavage event of PGA results in multiple-release of 5-amino-2-nitro-benzoic acid reporter units and a generation of a strong yellow color. The polymeric molecule is designed to be water-soluble since the reporter groups contain a carboxyl-acid group that is ionized under physiological conditions.

In a similar manner, other reporter groups with primary or secondary amine group can be used for the generation of UV, UV-vis or fluorescence signals. The preparation of such polymers can be carried out following similar procedures for the preparation of self-immolative dendrons as reported in WO 2004/019993.

EXAMPLE 7 Preparation of self-immolative polymers with a chemotherapeutic agent as a releasable group

Macromolecules (>20,000) are known to accumulate selectively at tumor sites due to the enhanced permeability and retention (EPR) effect. This effect occurs due to the difference between the vasculature physiology of solid tumors and normal tissues. Compared with the regular ordered vasculature of normal tissues, blood vessels in tumors are often highly abnormal. The growth of the tumor creates a constant need for the continuous supply of new blood vessels. This process, termed angiogenesis, often results in the construction of vessels with leaky walls, which allows enhanced permeability of macromolecules within the tumor. In addition, poor lymphatic drainage at the tumor site promotes accumulation of large molecules. Figure 12 presents a schematic illustration of the activation and subsequent cascade break-down of an exemplary self-ϊmmolative comb polymer according to embodiments of the present invention (Compound 20), which releases a plurality of molecules of the anticancer drug doxorubicin (DOX) after a single triggering event effected by penicillin-G-amidase (PGA) which cleaves off the cleavable triggering unit phenylacetamide (marked in red).

The preparation of Compound 20 is performed using the procedure discussed in

Example 3 hereinabove and presented in Figure 9. The DOX molecules are attached to the polymeric backbone following similar procedures for the preparation of self-immolative dendrons, as reported in WO 2004/019993, thereby affording a single-triggered self- immolative comb polymer which carries a plurality of releasable drug molecules.

EXAMPLE 8 Introduction of various drug molecules into self-immolative polymers

Others drugs with available amine functional group, such as, for example, melphalan, can be attached to a self-immolative polymer by a similar process according to the present embodiments.

Replacing phenylacetamide, the PGA substrate, by a specific peptide which is cleavable by endogenous enzymes, such as cathepsin-B, affords a polymeric prodrug for in vivo evaluation. When using a self-immolative polymer vehicle for drug delivery one should evaluate the toxicity of the polymer building blocks. It is known that azaquinone-methide is a highly reactive species and therefore, can exhibit in vivo toxicity by reacting with nucleophilic amino- acid residues of proteins. However, the polymer-drug conjugate is expected to stay intact until it targets the blood vessels of the tumor through the EPR effect. There, an endogenous protease like cathepsin-B will trigger the self-immolative disassembly process and release the drug molecules. Since at this point the self-immolative polymer is already at the tumor site, additional toxicity by the azaquinone-methide could even be desirable.

EXAMPLE 9 Introduction of the drug camptothecin into self-immolative polymers

In order to incorporate reporter groups, which do not exhibit an amine group, into the self-immolative polymers as described herein, other inherent functional group of the drug can be employed. For example, the anti-cancer agent camptothecin has an active hydroxy functionality. Figure 13 presents a schematic illustration of a procedure for converting camptothecin (Compound 21) into a suitable reporter group according to embodiments of the present invention, by using N,N-dimethylethy!ene-diamine as a self-immolative spacer, linking between a hydroxy functional of a drug molecule, and the polymeric backbone. As can be seen in Figure 13, the N,N-dimethylethylene-diamine spacer protects the hydroxy group of the drug molecule while presenting a free amine functionality in its place. When this spacer is removed, the hydroxy group of the drug molecule is released through a spontaneous cyclization reaction in which N.N-dimethyl urea derivative is formed.

The introduction of camptothecin can be carried out following similar procedures for the preparation of self-immolative dendrons as reported in WO 2004/019993.

EXAMPLE 10

Preparation of water soluble self-immolative polymers

One desirable feature of the polymeric systems described herein is to have water solubility. For example, drug delivery and diagnosis applications often require aqueous working conditions.

Water-soluble polymeric systems are prepared via two possible courses, as follows. Releasable units having a hydrophilic group may be linked to the polymeric backbone such that the hydrophilic group does not participate in the linkage and hence remains free and contributes to hydrophilicity of the resulting polymer. This approach is applicable only for specific releasable units that posses two such chemical functionalities, namely one for attachment and one for hydrophilicity.

Releasable units or reporter groups with hydrophilic polar groups like the carboxyl of reporter group Compound 19 (see, Figure 11) form a hydrophilic polymeric backbone. Similarly, anticancer drugs like melphalan that have carboxy-acid functionality are also suitably functionalized for this purpose.

Alternatively, or in addition, hydrophilic moieties (e.g., ethylene glycol) can be attached to the polymer backbone through a stable ether linkage. These molecules are attached to the backbone unit at one position and the reporter groups are attached at another, preferably distal, position. Figure 14 presents a schematic illustration of an exemplary water-soluble seif- immolative comb polymer wherein hydrophilic moieties (marked in green) are attached thereto in a similar manner to the attachment of the reporter groups (marked in blue).

The self-immolative polymers presented herein can be designed to be more water- soluble by, for example, containing a carboxyl moiety substitution on the building units, rendering the polymer ionizable under physiological conditions. The synthesis of such an exemplary water-soluble polycarbamate-based self-immolative polymer is illustrated in Scheme 5 below:

mol 15 min 10 eq.

phenyl 2-((E)-3-(iert- butoxycarbonyl)prop-1-enyl)-4-

(hydroxymethyl)phenylcarbamate Phenyl 2-((E)-3-(tert-butoxycarbonyl)prop-1-enyl)-4-(hydroxymethyl)phenyl carbamate (150 mg, 0.406 mmol) was suspended in toluene and heated for 15 minutes at 110 ⁰C in the presence of DBTL (7 μl, 0.01 mmol, 2.5 % mol). Thereafter, 4-hydroxy-2- butanone (90 μl, 1.01 mmol, 2.5 equivalents) was added and the reaction was stirred for another 30 minutes at 110 ⁰C. The reaction was cooled to room temperature and the polymer was precipitated by the addition of MeOH. The suspension was filtered and the polymer was dried under reduced pressure for 24 hours.

The te/f-butyl ester protected polymer was obtained as a white powder (75-100 mg, 50-65 % yield). 1H-NMR (200MHz, DMSOd₆): δ = 9.58 (s, 22H), 7.75-7.85 (m, 2H), 7.65 (s, 22H),

6.43 (d, J = 16Hz, 11H), 5.11 (s, 22H), 4.35 (d, J = 5.6Hz, 2H), 4.23 (t, J = 6.0Hz 2H), 3.82 (t, J = 6.0Hz, 2H), 2.10 (s, 3H), 1.44 (s, 99H).

The fe/t-butyl ester protected polymer was taken in a mixture of TFA and DCM (1:1 ratio) and stirred at room temperature for 5 minutes. The solvents were immediately removed under reduced pressure and the polymer was dried for another 24 hours.

The water soluble polymer contained 11 monomeric building units and was obtained as a yellowish solid in quantitative yield.

¹H-NMR (200MHz, DMSOd₆): δ = 9.55 (s, 22H), 7.70-7.80 (m, 2H), 7.57 (s, 22H), 6.43 (d, J = 16Hz, 11H), 5.09 (s, 22H), 4.35 (d, J= 5.6Hz, 2H), 4.23 (t, J = 6.0Hz, 2H), 3.82 (t, J = 6.0Hz, 2H), 2.10 (s, 3H).

EXAMPLE 11 Disintegration of a water soluble self-immolative polymer

The disassembly of the water-soluble self-immolative polymer presented in the previous example, effected by an enzymatic triggering event (enzymatic removal of the biocleavable triggering unit) and the release of a fluorogenic molecule (Compound IV), derived from the building unit, is illustrated in Scheme 6 below.

Scheme 6

The disintegration product, (4-amino-3-((E)-3-(carboxylic acid)prop-1- enyl)phenyl)methanol (Compound IV), is by itself a fluorogenic compound. Figure 16 presents a plot of the fluorescence change monitored during the disintegration process of the exemplary water-soluble self-immolative polymer (concentration 500 μM) at λem of 500 nm (λex = 270 nm, marked in circles in Figure 16), triggered by the enzymatic cleavage of the end carbamate. The disintegration experiment was conducted in borax buffer solution pH 8.5 containing BSA (10 mg/ml) which was also used as a blank solution for calibration (marked in squares in Figure 16).

EXAMPLE 12

Self-immolation of a self-immolative oligomer with PGA substrate as a trigger and tryptophan as a releasable unit (Compound 23)

According to an embodiment of the present invention, another exemplary carbamate- based self-immolative polymer, having the cleavable triggering unit phenylacetamide and the releasable unit tryptophan was prepared. This exemplary self-immolative polymer was designed to disintegrating after a triggering event effected by the enzyme penicillin-G- amidase (PGA). The preparation of such a polymer, Compound 23, is illustrated in Scheme 7 below. Scheme 7

U D^rM^ypF^l,⁰6^P0^h0aGⁿ,^e O'^B.N³.^N

Compound 23

Preparation of 4-[(tert-hutyldimethylsilyloxy)methyl]aniline (Compound A): A- Aminobenzyl alcohol (1.5 grams, 12.18 mmol, 1 equivalent) and imidazole (830 mg, 12.18 mmol, 1 equivalent) were dissolved in DMF and cooled to 0 ⁰C. Thereafter TBDMS-CI (1.836 grams, 12.18 mmol, 1 equivalent) was added and the reaction stirred for 15 minutes at room temperature. EtOAc was then added, the organic phase washed with saturated NH4CI and dried over MgSO4. Flash chromatography afforded the protected alcohol Compound A (2.36 grams, 82 % yield, CAS No. 131230-76-7).

Preparation of Compound B: Compound A (500 mg, 2.1 mmoi) was added dropwise over a period of 10 minutes to a solution of toluene (30 ml) and phosgene (1M in toluene, 21 ml, 21 mmol, 10 equivalents) at 110 ⁰C. The reaction was stirred for 10 minutes and the toluene evaporated under reduced pressure. The isocyanate, obtained as colorless oil, was dissolved again in toluene (10 ml), heated to 100 ⁰C, and then DBTL (35 μl, 0.05 mmol, 2.5 % mol) and N-[4-(hydroxymethyl)phenyl]-benzeneacetamide (506 mg, 2.1 mmol, 1 equivalent) were added. The reaction was monitored by TLC. Upon completion, the product was purified by flash chromatography to yield the dimer Compound B (794 mg, 75 % yield).

¹H-NMR (200 MHz, DMSO-d6): δ = 10.15 (s, 1H), 9.59 (s, 1 H), 7.53 (d, J = 7.2Hz ,2H), 7.10-7.37 (m, 11H), 4.98 (s, 2H), 4.35 (s, 2H), 3.55 (s, 2H), 0.80 (s, 9H)₁ 0.01 (s, 6H).

Preparation of Compound C: Compound B (795 mg, 1.57 mmol, 1 equivalent) was dissolved in MeOH and AMBERLYST® 15 (an ion-exchange resin by GFS Chemicals, CAS No. 39389-20-3) was added. The reaction was monitored to completion by TLC, then the AMBERLYST® 15 beads were filtered out and the solvent evaporated. Flash chromatography afforded the alcohol Compound C (581 mg, 95 % yield) as a white solid. ¹H-NMR (200 MHz, DMSO-d6): δ = 10.15 (s, 1H), 9.58 (s, 1H), 7.53 (d, J = 7.2Hz ,

2H)₁ 7.12-7.36 (m, 11H), 4.96 (s, 2H), 4.32 (s, 2H), 3.54 (s, 2H).

Preparation of Compound D: Compound A (355 mg, 1.5 mmol, 1 equivalent) was added drop wise over a period of 10 minutes to a solution of toluene (20 ml) and phosgene (1M in toluene, 15 ml, 15 mmol, 10 equivalents) at 110 ⁰C. The reaction was stirred for 10 minutes and the toluene evaporated under reduced pressure. The isocyanate, obtained as colorless oil, was dissolved again in toluene (10 ml), heated to 110 ⁰C, and DBTL (22 μl, 0.037 mmol, 2.5 % mol) and N-[4-(hydroxymethyr)phenylj-benzeneacetamide (584 mg, 1.5 mmol, 1 equivalent) were added thereto. The reaction was monitored by TLC. Upon completion, the product was purified by flash chromatography to yield the trimer Compound D (636 mg, 65 % yield) as white solid.

¹H-NMR (200 MHz, DMSO-d6): δ = 10.14 (s, 1H), 9.71 (s, 1H), 9.67 (s, 1H), 7.53 (d, J = 7.2Hz, 2H), 7.13-7.41 (m, 15H), 4.99 (s, 2H), 4.97 (s, 2H), 4.38 (s, 2H), 3.61 (s, 2H), 0.82 (s, 9H), 0.01 (s, 6H). Preparation of Compound E: Compound D (651 mg, 0.97 mmol, 1 equivalent) was dissolved in MeOH and AMBERLYST® 15 was added thereto. The reaction was monitored to completion by TLC, then the AMBERLYST® 15 beads were filtered out and the solvent evaporated under reduced pressure. Flash chromatography afforded Compound E (497 mg, 95 % yield) as a white solid. 1H-NMR (200 MHz, DMSO-d6): δ = 10.16 (s, 1 H), 9.71 (s, 1H), 9.65 (s, 1H), 7.53 (d,

J = 7.2Hz, 2H), 7.11-7.40 (m, 15H), 4.99 (s, 2H), 4.97 (s, 2H), 4.32 (s, 2H), 3.59 (s, 2H).

Preparation of Compound F: A mixture of Compound E (300 mg, 0.57 mmol, 1 equivalent), p-nitrophenylchlorophormate (345 mg, 1.71 mmol, 3 equivalents), DIPEA (397 μl, 2.28 mmol, 4 equivalents) and pyridine (4.5 μl, 0.057 mmol, 0.1 equivalent) was stirred in dry THF under argon atmosphere. The reaction was monitored by TLC. Upon completion, EtOAc was added, the organic phase washed with saturated NH4C1, and then dried over MgSO4. The product was purified by flash chromatography to afford Compound F (305 mg, 76 % yield) as yellowish solid.

¹H-NMR (200 MHz, DMSO-d6): δ = 10.15 (s, 1H), 9.71 (s, 1H), 9.63 (s, 1H), 8.28 (d, J = 8.2Hz, 2H), 7.53 (d, J = 7.2Hz, 2H), 7.11-7.40 (m, 17H), 4.99 (s, 2H), 4.97 (s, 2H), 4.32 (s, 2H), 3.59 (s, 2H).

Preparation of the self-immolative polymer Compound 23: Compound F (250 mg, 0.355 mmol, 1 equivalent) was dissolved in DMF and L-tryptophane (218 mg, 1.065 mmol, 3 equivalents) and Et₃N (5 μl, 0.035 mmol, 0.1 equivalent) were added thereto. The reaction was heated to 60 ⁰C and left to stir for 12 additional hours. Thereafter, the solvent was evaporated under reduced pressure and the residue was purified by flash chromatography to afford the self-immolative polymer Compound 23 (185 mg, 68 % yield) as yellowish solid.

¹H-NMR (200 MHz, DMSO-d6): δ = 10.75 (s, 1H), 10.16 (s, 1H), 9.72 (s, 1H), 9.67 (s, 1H), 7.86 (s, 1 H), 6.80-7.55 (m, 21H), 4.99 (s, 2H), 4.97 (s, 2H), 4.79.(d, J = 4.4Hz, 2H), 4.10 (m, 1 H), 3.56 (s, 2H). Figure 15 presents a chemical scheme of a PGA-triggered release of tryptophan through an exemplary self-immolative trimer according to the present embodiments. As can be seen in Figure 15 the trimeric self-immoiative oligomer (Compound 23) having a PGA substrate as a cleavable triggering unit (marked in blue in Figure 15) and tryptophan as a reporter group (marked in red in Figure 15) was prepared using the procedures described hereinabove.

A stock solution of Compound 23 in DMSO was prepared to a final concentration of 5 mM. 5 L from this stock solution were added to 95 L of PBS pH 7.4 containing the protein BSA at a concentration of 1 mg/ml. A second sample was prepared by using PBS that contained no BSA and served as a reference. The samples were injected to the HPLC in parallel time intervals and the absorbance intensity of the released p-nitroaniline (PNA) was measured. After 90 minutes the release of PNA was completed from the sample that contained the protein BSA.

Figures 17A-B present comparative plots following the release of p-nitroaniline and tryptophan effected by the enzymatically catalyzed disintegration of Compound 23, following the increase in the absorbance intensity ( _max=378) representing the release of p-nitroaniline by the catalytic triggering event effected by BSA (blue line in Figure 17A), as compared to the absorbance intensity change in the control solution that contains no protein (red line in Figure 17A), and by following the conversion of Compound 23 (red line in Figure 17B) to tryptophan (blue line in Figure 17B) as monitored via HPLC.

As can be seen in Figures 17A and 17B, the release of free tryptophan was observed facilely, and completed within seconds. Since PGA is a protease that cleaves the phenylacetamide group specifically, the intermediate Compound 24 was formed initially and subsequently disassembled rapidly into hydrolyzed azaquinone-methide molecules and tryptophan.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.

Claims

WHAT IS CLAIMED IS:

1. A polymer comprising at least one cleavable triggering unit, at least one releasable unit and a plurality of building units, said plurality of building units being linked to one another so as to form a self-immolative polymeric backbone which carries said cleavable triggering unit and said releasable unit, each of said building units in said self-immolative polymeric backbone independently has a general formula selected from the group consisting of Formula Ia and Formula Ib:

Formula Ia Formula Ib

wherein:

V is O, S, PR⁶ or NR⁷; U is O, S or NR⁸;

A, B, D and E are each independently a carbon atom or a nitrogen atom; R¹, R², R³, R⁴ and R⁵ are each independently

cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalornethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, or alternatively, at least two of R¹, R², R³, R⁴ and R⁵ being connected to one another to form an aromatic or aliphatic cyclic structure; whereas: . a, b and c are each independently as integer of 0 to 5;

K is O, S, PR⁶ or NR⁷; and

I, F and G are each independently -R¹¹C=CR¹²- or -C≡C-, where each of R¹¹ and R¹² is independently hydrogen, alky!, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, or, alternatively, R¹¹ and R¹² being connected to one another to form an aromatic or aliphatic cyclic structure; and

R⁶, R⁷ and R⁸ are each independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, provided that at least one of R¹-R³ in Formula Ia and of R¹ -R⁵ in Formula Ib is said

said cleavable triggering unit and said self-immolative polymeric backbone being such that upon cleavage of said cleavable triggering unit, said self-immolative polymeric backbone self-immolates, thereby releasing said at least one releasable unit.

2. A polymer comprising at least one cleavable triggering unit, at least one releasable unit and a plurality of building units, said plurality of building units being linked to one another so as to form a self-immolative polymeric backbone, said polymeric backbone carrying said cleavable triggering unit and said releasable unit, said cleavable triggering unit and said self-immolative polymeric backbone being such that upon cleavage of said cleavable triggering unit, said self-immolative polymeric backbone self-immolates, thereby releasing said at least one releasable unit.

3. The polymer of any of claims 1 and 2, comprising a plurality of releasable units, said releasable units being the same or different.

4. The polymer of any of claims 1 and 2, comprising a plurality of cleavable triggering units, said cleavable triggering units being the same or different.

5. The polymer of claim 4, wherein said cleavable triggering units are different, and at least two of said cleavable triggering units are cleavable upon a different event.

6. The polymer of any of claims 1 and 2, further comprising at least one self- immolative spacer.

7. The polymer of claim 6, wherein said spacer links said at least one cleavable triggering unit and at least one of said building units in said self-immolative polymeric backbone.

8. . The polymer of claim 6, wherein said at least one spacer links at least one of said releasable units and at least one of said building units in said self-immolative polymeric backbone.

9. The polymer of claim 6, wherein said spacer links at least two of said building units.

10. The polymer of claim 6, wherein said at least one cleavable triggering unit, said at least one spacer and said building units being such that upon cleavage of said at least one cleavable triggering unit, said self-immolative polymeric backbone and said at least one spacer self-immolate to thereby release said at least one releasable unit.

11. The polymer of any of claims 1-10, wherein at least one of said building units in said self-immolative polymeric backbone has at least two releasable units linked thereto.

12. The polymer of any of claims 1 and 2, wherein each of said building units in said self-immolative polymeric backbone has at least two releasable units attached thereto.

13. The polymer of any of claims 1 and 2, wherein said at least one cleavable triggering unit is selected from the group consisting of a photo-labile triggering unit, a chemically removable triggering unit, a hydrolizable triggering unit and a biocleavable triggering unit.

14. The polymer of any of claims 1 and 2, wherein said at least one releasable unit is selected from the group consisting of a detectable agent, a therapeutically active agent, a second self-immolative compound, a chemosensitizing agent, a targeting moiety, an agrochemical, a chemical moiety and a chemical reagent.

15. The polymer of claim 13, wherein said at least one cleavable triggering unit is a biocleavable triggering unit and said at least one releasable unit comprises an agent selected from the group consisting of a therapeutically active agent, a chemosensitizing agent, a targeting moiety and a detectable agent.

16. The polymer of claim 15, wherein said biocleavable triggering unit is an enzymatically cleavable triggering unit.

17. The polymer of claim 15, wherein said therapeutically active agent is a chemotherapeutic agent.

18. The polymer of claim 13, wherein said at least one cleavable triggering unit is a photo-labile triggering unit and said releasable unit comprises a detectable agent.

19. The polymer of claim 13, wherein said at least one cleavable triggering unit is a hydrolyzable triggering unit and said releasable unit comprises an agrochemical.

20. The polymer of claim 13, wherein said at least one cleavable triggering unit is a chemically removable triggering unit and said releasable unit comprises a detectable agent.

21. The polymer of claim 14, wherein said detectable agent is selected from the group consisting of fluorescent agent, a radioactive agent, a magnetic agent, a chromophore, a phosphorescent agent, a contrast agent and a heavy metal cluster.

22. The polymer of any of claims 1 and 2, wherein said self-immolative polymeric backbone is selected from the group consisting of a polycarbamate, a polycarbonate, a polyether and a polyurethane.

23. The polymer of claim 2, wherein each of said building units in said self- immolative polymeric backbone independently has a general formula selected from the group consisting of Formula Ia and Formula Ib:

Formula Ia Formula Ib

wherein:

V is O₁ S, PR⁶ or NR⁷;

U is O₁ S or NR⁸;

A, B, D and E are each independently a carbon atom or a nitrogen atom;

R¹, R², R³, R⁴ and R⁵ are each independently

_ hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, or alternatively, at least two of R¹, R², R³, R⁴ and R⁵ being connected to one another to form an aromatic or aliphatic cyclic structure; whereas: a, b and c are each independently as integer of 0 to 5;

K is O, S₁ PR⁶ or NR⁷; and

I, F and G are each independently -R¹¹C=CR¹²- or -CsC-, where each of R¹¹ and R¹² is independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkyiamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazoie, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, or, alternatively, R¹¹ and R¹² being connected to one another to form an aromatic or aliphatic cyclic structure; and

R⁶, R⁷ and R⁸ are each independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, provided that at least one of R¹-R³ in Formula Ia and of R¹-R⁵ in Formula Ib is said

24. The polymer of any of claims 1 and 23, wherein at least one of said building units has the general Formula Ib.

25. The polymer of claim 24, wherein: V is O or S; each of B and D is a carbon atom; each of R¹, R² R⁴ and R⁵ is independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, or alternatively, at least two of R², R³ and R⁴ being connected to one another to form an aromatic or aliphatic cyclic structure; and R³ is said

26. The polymer of claim 25, wherein: each of R¹, R² R⁴ and R⁵ is independently hydrogen or alky!; each of a, b and c equal 0; and each of R⁹ and R¹⁰ is independently hydrogen or alkyl.

27. The polymer of claim 6, wherein said self-immolative spacer has a general formula selected from the group consisting of Formula Ha, Formula lib, Formula Hc, Formula lid:

Formula Ha Formula Hb

Formula Uc Formula Hd

and a combination thereof, wherein: d, e, f, g and h are each independently an integer from 0 to 3, provided that d + e + f > 2;

R¹² and R¹³ are each independently hydrogen, alkyl or cycloalkyl; and

R¹⁴, R¹⁵, R¹⁶, R¹⁷, R¹⁸ and R¹⁹ are each independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyi, phosphonooxy or phosphate.

28. The polymer of any of claims 1 and 2, having a general formula selected from the group consisting of:

Q - A₁ - [X-Y]n -A₂ - W Q - A₁ - [X(W)m-Y]n-1 - Xn

Formula Ilia Formula IHb

wherein: n is an integer from 2 to 10⁵; m is an integer from 1 to 4;

Q is said cleavable triggering unit;

A₁ and A₂ are each independently said seif-immoiative spacer or absent;

X is said building unit;

Y is said self-immolative spacer or absent; and

W is said releasable unit.

29. A polymer comprising a plurality of building units linked to one another, each of said building units independently having a general formula selected from the group consisting of Formula Ia and Formula Ib:

Formula Ia Formula Ib

wherein:

V is O, S, PR⁶ or NR⁷;

U is O, S or NR⁸;

A₁ B, D and E are each independently a carbon atom or a nitrogen atom;

R¹, R², R³, R⁴ and R⁵ are each independently

_t hydrogen, alky!, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, or alternatively, at least two of R¹, R², R³, R⁴ and R⁵ being connected to one another to form an aromatic or aliphatic cyclic structure; whereas: a, b and c are each independently as integer of 0 to 5;

K is O, S, PR⁶ or NR⁷; and

I₁ F and G are each independently -R¹¹C=CR¹²- or -C≡C-, where each of R¹¹ and R¹² is independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkylpiperazinyl, morpholino, tetrazole, carboxy, carboxylate, suifoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, or, alternatively, R¹¹ and R¹² being connected to one another to form an aromatic or aliphatic cyclic structure; and

R⁶, R⁷ and R⁸ are each independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkyipiperazinyl, morpholino, tetrazole, carboxy, carboxylate, suifoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, provided that at least one of R¹-R³ in Formula Ia and of R¹-R⁵ in Formula Ib is said

30. The polymer of claim 29, wherein each of said building units has the general Formula Ib.

31. The polymer of claim 30, wherein: V is O or S; each of B and D is a carbon atom; each of R¹, R², R⁴ and R⁵ is independently hydrogen, alkyl, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, alkoxy, hydroxy, thiohydroxy, thioalkoxy, aryloxy, thioaryloxy, amino, nitro, halo, trihalomethyl, cyano, C-amido, N-amido, cyclic alkylamino, imidazolyl, alkyipiperazinyl, morpholino, tetrazole, carboxy, carboxylate, sulfoxy, sulfonate, sulfonyl, sulfixy, sulfinate, sulfinyl, phosphonooxy or phosphate, or alternatively, at least two of R², R³ and R⁴ being connected to one another to form an aromatic or aliphatic cyclic structure; and R³ is said

32. The polymer of claim 31 , wherein: each of R¹, R², R⁴ and R⁵ is independently hydrogen or alkyl; each of a, b and c equal 0; and each of R⁹ and R¹⁰ is independently hydrogen or alkyl.

33. A composition comprising the polymer of any of claims 1-28.

34. The composition of claim 33, wherein said releasable unit comprises a therapeutically active agent and said cleavable triggering unit is a biocleavable triggering unit, the composition being a pharmaceutical composition which further comprises a pharmaceutically acceptable carrier.

35. The composition of claim 34, wherein said at least one therapeutically active agent is selected from the group consisting of an anti-proliferative agent, an anti-inflammatory agent, an antibiotic, an anti-viral agent, an anti-hypertensive agent, a chemosensitizing agent and a combination thereof.

36. The composition of claim 35, being packaged in a packaging material and identified in print, in or on said packaging material, for use in the treatment of a disease or disorder treatable by said therapeutically active agent.

37. The composition of claim 33, wherein said releasable unit is a detectable agent, the composition being for use in a diagnostic and/or analytical application.

38. The composition of claim 33, wherein said releasable unit is an agricultural agent and said cleavable triggering unit is a hydrolyzable triggering unit, the composition being an agricultural composition which further comprises an agriculturally acceptable carrier.

39. An article-of-manufacture comprising the polymer of any of claims 1-32.

40. The article-of-manufacture of claim 39, being selected from the group consisting of a medical device, a disposable plastic product, a disposable women's sanitary item, a diaper, a disposable medical supply, a disposable food container or dish, a disposable item of clothing and a disposable cutlery item.

41. Use of the composition of claim 34 as a medicament for treating a condition that is treatable by said therapeutically active agent.

42. A process of preparing the self-immolative polymer of any of claims 1-28, the process comprising: polymerizing said plurality of building units; attaching said at least one releasable unit to at least one of said plurality of building units; and attaching said at least one cleavable triggering unit to said polymeric backbone.

43. The process of claim 42, wherein attaching said at least one releasable unit to at least one of said plurality of building units is performed prior to said polymerizing.

44. The process of claim 42, wherein at least one of said plurality of building units has at least one building unit attached thereto prior to said polymerizing.

45. The process of claim 44, wherein attaching said at least one releasable unit to at least one of said plurality of building units is performed prior to said polymerizing.